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Dissertations / Theses on the topic 'Microbial inhibition'
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1
Townson, Iwan Meredydd. "Microbial inhibition of methane clathrate hydrates." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/41022.
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Two microbial species were tested for inhibition of methane hydrates in a stirred crystallizer (subcooling of 2.34 K). The ice associating Chryseobacterium sp. Strain C14, grown in 0.5 wt% Tryptic Soy Broth (TSB) delayed hydrate nucleation, on average, by 30.3 hours compared to 37.9 hours for the PVP solutions. Escherichia coli TG2 in 0.5 wt% TSB was used as a non ice associating bacteria control and surprisingly had the longest induction period of 118.1 hours, suggesting that it was 3 times more effective as a hydrate inhibitor than PVP. The 0.5 wt% aq. TSB solution without bacteria delayed hydrate nucleation an average of 6.7 hours, whilst bacteria without TSB also showed significant inhibition. However, for the bacteria and bacteria + TSB systems, nucleation times were far more sporadic and time dependant than the simple systems of pure water and PVP. PVP decreased hydrate growth rate but increased gas consumption by nearly 4 fold. TSB without bacteria promoted gas consumption by over 2 fold but exhibited a slightly higher growth rate than the pure water solution. Reasons for the differences in growth profiles may be a result of the observed morphological differences in the hydrate phase. Chryseobacterium in 0.5 wt% aq. TSB had a distinct time dependency in growth characteristics and promoted growth rate almost 3 fold. E. coli in 0.5 wt% TSB showed a unique S-curve growth profile where the initial growth rate was very low. The differences in growth profiles of the two bacteria suggest different inhibition mechanisms. Ice-associating proteins likely play a significant role in hydrate formation, especially for Chryseobacterium which has shown inhibition of ice recrystallization. However, the interaction of other non-ice associating macromolecules may play a primary role in the observed inhibition and that biofilm formation may act as a barrier between the gas-liquid and/or heterogeneous nucleating solid-liquid interfaces which may help explain the significant inhibition observed by E. coli. Considering that both species of bacteria yielded significant hydrate inhibition, albeit somewhat unpredictable, but since the procedure is simple, the potential of employing bacteria as ‘Microbial Hydrate Inhibitors’ looks promising. However, consistent inhibition
will be a challenge to overcome so that these organisms could be used as other KHI solutions.
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Chuong, Amy (Amy S. ). "Noninvasive optical inhibition with a red-shifted microbial rhodopsin." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98648.
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Thesis: Ph. D., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references.
Optogenetic inhibition of neurons enables the causal assessment of their contributions to brain functions, but a limit to the utility of optogenetic modulation is the quantity of neural tissue that can be successfully addressed from a given optical source. Previous optogenetic inhibitors are driven by blue, green, or yellow wavelengths, all of which suffer substantial light power attenuation as a result of tissue and hemoglobin optical absorption. In this thesis, I describe the discovery, engineering, and implementation of a new red-shifted cruxhalorhodopsin, Jaws, derived from Haloarcula salinarum (strain Shark), which mediates three-fold higher red light-induced photocurrents than other inhibitory opsins. I describe the design process involved in engineering Jaws, as well as its characterization in vitro, ex vivo, within the awake in vivo rodent brain, and in transgenic mice. Jaws exhibits robust inhibition of sensory-evoked neural activity in the cortex and results in strong light responses when used in retinas of retinitis pigmentosa model mice. Finally, I demonstrate that Jaws can mediate transcranial optical silencing of neurons deep in the brains of awake mice. The noninvasive optogenetic inhibition opened up by Jaws enables a variety of important neuroscience experiments, and offers a powerful general-use chloride pump for basic and applied neuroscience.
by Amy S. Chuong.
Ph. D.
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Bown, R. P. A. "Inhibition of TEM-2 #beta#-lactamase by clavulanate." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308705.
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Mosneaguta, Ruslan. "The effect of chemical preservatives on inhibition of potato browning, volatile organic compounds profile, and microbial inhibition." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1339015151.
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Dyckman, Samantha Katherine. "Microbial Interactions: Prediction, Characterization, and Spatial Context." Thesis, Boston College, 2021. http://hdl.handle.net/2345/bc-ir:109218.
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Thesis advisor: Babak MomeniMicrobial communities are complex networks comprised of multiple species that are facilitating and inhibiting one another (as well as themselves). Currently, we lack an understanding of what mechanisms drive coexistence within these communities. We aimed to remedy this by studying the dynamics of coexisting communities, focusing on the complexity of their interaction networks, the impact of spatial dynamics, and the interplay of facilitating and inhibiting interactions. These limitations in our understanding prevent the furtherment of designing intentional communities for bioremediation, maintenance of healthy microbiota, and other functional communities. To better understand these microbial dynamics, we chose to address the problem from two fronts: computational modeling and exploring dynamics of cocultures. Through our 1-D model, spatial structure fostering more coexistence – especially when facilitation is present. For the coexistence assays, we determined that contact-dependent growth inhibition is a density dependent mechanism, and the use of a Tn-Seq mutant library to predict species interactions is possible, but needs further optimization to reconcile density dependent effects of interactions
Thesis (MS) — Boston College, 2021
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Biology
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Filek, Klara. "Contact-dependent growth inhibition in Escherichia coli EC93." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355533.
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Microorganisms live in complex communities and interact either through secreting soluble molecules or by delivering effectors in a contact dependent manner. Microbial interactions range from cooperative to competitive. Contact-dependent growth inhibition (CDI), discovered in Escherichia coli EC93, is becoming increasingly studied, as this mode of interaction seems to be widespread among proteobacteria. CDI is mediated by cdiBAI genes which encode for a two-partner secretion system; i.e. CdiB is an outer membrane protein that transports CdiA to the surface of the cell. CdiA can interact with a specific receptor on a target cell and deliver a toxin localized in its C-terminal domain to the target cell. CdiI is a small immunity protein that neutralizes the toxic effect of CdiA toxin. Recently, evidence from our research group has shown that E. coli EC93 harbours two cdi loci. The first cdi locus has been extensively studied but the role of second locus remained unknown. In this study we wanted to elucidate the activity and the role of second E. coli EC93 cdi locus in intra-strain bacterial interactions. Bacterial competitions of E. coli EC93 wild type versus E. coli EC93 targets that had deletions for one or both cdi loci showed that the second locus is indeed active in inhibiting the targets, albeit to a lesser extent than the first. The toxic activity of the second cdi-locus was neutralized specifically by the second immunity protein. The expression of both these systems is higher under carbon starvation conditions than in nutrient rich conditions. Unfortunately, we could not elucidate the mechanism of toxicity for the second cdi locus toxin. Taken together, our results show that E. coli EC93 actively uses both of its cdi loci during bacterial interactions and that these systems are more active during stressful conditions.
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Chinnam, Naga babu. "Inhibition of Escherichia coli ATP Synthase Using Bioflavonoids." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etd/1298.
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ATP synthase is the fundamental means of the cellular energy production in all organisms. Malfunction of ATP synthase is associated with multiple disease conditions. This enzyme is not only implicated in disease conditions but also likely to contribute in new therapies for multiple diseases by being a molecular target for several inhibitors. Bioflavonoids are a class of plant secondary metabolites known to exhibit antioxidants, chemopreventive, and chemotherapeutic properties. Their actual mode of action is not clear; however, some bioflavonoid are known to block the action of enzymes and other substances that promote the growth of cancer cells by binding to the multiple molecular targets in the body including ATP synthase. The most common dietary polyphenol resveratrol was shown to induce apoptosis via mitochondrial pathways and has chemopreventive properties against prostate cancer. Here we report the general inhibitory effects of dietary bioflavonoids on ATP synthase enzyme and intact E. coli cells.
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Ruiz, Rueda Cristian. "Microbial lipases with interest in biotechnology and infectious diseases: isolation, characterization and inhibition by natural substances." Doctoral thesis, Universitat de Barcelona, 2005. http://hdl.handle.net/10803/2401.
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Lipases are carboxylic ester hydrolases which act on acylglycerols to liberate fatty acids and glycerol. These enzymes are currently attracting an enormous attention because they are among the most versatile and widely used enzymes in biotechnological applications and due to their unique properties. Moreover, these enzymes and their inhibitors have a high pharmacological interest because some microbial lipases can act as virulence factors in several infectious diseases. Therefore, the general objective of the present work was the isolation, cloning, characterization and inhibition by natural substances of microbial lipases with interest in biotechnology and infectious diseases.The first chapter was focused on the isolation and characterization of new Bacillus lipases to evaluate their biotechnological potential. The lipolytic system of several very active strains with an unknown lipolytic system was analyzed, and then, the lipases LipA from Bacillus megaterium CECT 370 and LipA from Bacillus sp. BP-6 were isolated, cloned and characterized. Both enzymes are family I.4 carboxylesterases closely related to Bacillus subtilis LipB, and have a high biotechnological potential due to their high stability and due to their molecular and biochemical properties.
Chapter 2 consisted in the isolation of 724 microorganisms from soil samples collected from a subtropical forest of Puerto Iguazú (Argentina). Among them, 449 showed one or more of the biotechnologically-interesting enzymatic activities "true lipase", carboxylesterase, cellulase, xylanase and pectinase. CR-53 and CR-179, two very active isolates, were subsequently identified as two strains closely related to the species Rhodococcus erythropolis and Bacillus subtilis, respectively. Further analysis revealed that strain CR-53 produces a cell-bound carboxylesterase of 60 kDa, one of the first lipases known in the genus Rhodococcus, whereas strain CR-179 possesses a lipolytic system related to that of other Bacillus.
Chapter 3 was focused in the development of a new, fast, simple and more sensitive colorimetric microassay with a low cost and suitable for high-throughput analysis of purified or non-purified lipolytic enzymes. The assay was subsequently used to evaluate the effect of several saturated fatty acids on five cell-bound or secreted (Paeni)Bacillus lipases. These lipids inhibited all the enzymes analyzed, although secreted lipases were activated by low concentrations of these compounds. Activation of microbial lipases by fatty acids is a phenomenon detected here for the first time, and could be related to the properties and biological function of these secreted enzymes.
Chapter 4 consisted in the analysis of the inhibitory effect of several natural substances (saponins, flavonoids and alkaloids) on the model lipase from Candida rugosa (CRL) to evaluate their potential as antilipase drugs. beta-aescin, digitonin, kaempferol and (±)-catechin were selected as the best candidates for the treatment or prevention of lipase-related diseases due to the strong inhibition they produced on CRL, as well as due to their other beneficial effects and their low toxicity.
The aim of chapter 5 was to isolate, clone, characterize and evaluate the inhibition of lipases from the pathogens Propionibacterium acnes and Helicobacter pylori. The analysis of GehA from Propionibacterium acnes P-37, a lipase considered as a major etiological agent in the pathogenesis of acne, revealed that this enzyme is very adapted to the skin conditions. EstV (HP0739), a family V carboxylesterase which was identified by analyzing Helicobacter pylori 26695 proteome, is the first lipase from this pathogen that has been cloned, purified and characterized. The evaluation of the effect of several natural substances on GehA and EstV revealed that beta-aescin, glycyrrhizic acid, (±)-catechin and kaempferol are promising candidates for the treatment of acne and/or ulcer due to their strong inhibitory activity on these lipases, as well as due to their other anctiacne or antiulcer effects and their low toxicity.
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Pietrzyk, Julian Darius. "Use of microbial consortia for conversion of biomass pyrolysis liquids into value-added products." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31562.
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Lignocellulosic biomasses are considered promising feedstocks for the next generation of biofuels and chemicals; however, the recalcitrance of lignocellulose remains a barrier to its utilisation over conventional sources. Pyrolysis is the heating of biomass to several hundred degrees Celsius in the absence of oxygen, which can thermally depolymerise lignocellulose. Products of pyrolysis are a solid biochar, liquid bio-oil and syngas. Biochar has roles in both carbon sequestration and soil amendment however bio-oil has no defined use, despite a high concentration of fermentable sugars. Bio-oil is a complex organic microemulsion with a host of biocatalyst inhibitors that makes its microbial degradation a challenge. In this work, the use of aerobic cultures using microbial communities isolated from natural environments saw limited potential; however, the use of anaerobic digestion (AD) successfully generated a higher volume of biogas from reactors with bio-oil than controls. Biogas yield test reactors were set up with anaerobic digestate from a wastewater treatment plant as the substrate for degradation and conversion of bio-oils. Next-generation 16S rRNA gene sequencing was utilised to characterise the communities in the reactors while the ultrahigh resolution mass spectrometry technique of Fourier transform ion cyclotron resonance (FT-ICR) was used for characterisation of the chemical changes occurring during AD. Both sets of high-resolution data were additionally combined for multivariate analysis and modelling of the microbial genera that correlated best with the changes in digestate chemistry. This represents a novel analysis method for the microbial degradation of complex organic products. Bio-oil from common lignocellulosic feedstock was the most easily degradable by the AD communities, with significant inhibition observed when bio-oils from anaerobic digestate and macroalgae were used. Additionally it was found that the inclusion of biochars that were pre-incubated in anaerobic digestate prior to use in AD were capable of significantly reducing the lag time observed for biogas production in bio-oil-supplemented reactors. The addition of biochars that were not pre-incubated had no effect on biogas production. Specific inhibition of methanogenesis was also capable of causing the digestates to accumulate volatile fatty acids (VFAs) as a product of greater value than biogas. Scale-up experiments will be required to confirm the precise practicalities of the addition of bio-oil to AD as well as to establish the potential for isolation and purification of VFAs.
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Howard, Michael D. "Investigation of Haemophilus somnus Virulence Factors: Lipooligosaccharide Sialylation and Inhibition of Superoxide Anion Production." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/26848.
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Virulent strains of the bovine opportunistic pathogen Haemophilus somnus (Histophilus somni) cause multi-systemic diseases in cattle. One of the reported virulence factors that H. somnus may use to persist in the host is resistance to intracellular killing. It is reported in this dissertation that H. somnus significantly (P <0.001) inhibited production of superoxide anion (O2-) by bovine mammary and alveolar macrophages as well as by polymorphonuclear leukocytes. Inhibition of O2- production was time- and dose-dependent and did not occur after incubation with Escherichia coli, H. influenzae, or Brucella abortus. Non-viable H. somnus, purified lipooligosaccharide (LOS), or cell-free supernatant from mid-log phase cultures did not inhibit O2- production, indicating that O2- inhibition required contact with live H. somnus. Commensal isolates of H. somnus were less capable or incapable of inhibiting macrophage O2- production compared to isolates tested from disease sites.
H. somnus shares conserved epitopes in its LOS with Neisseria gonorrhoeae, N. meningitidis, and H. influenzae, and can also undergo structural phase variation of these LOS epitopes. Sialylation of the terminal galactose of H. somnus LOS is another reported virulence mechanism. Current sequencing of the genomes of H. somnus strains 2336 (pathogenic) and 129Pt (commensal) has enabled in silico identification of three open reading frames (ORFs) involved in sialylation. The ORFs-1 (hsst-I) and -2 (hsst-II) had BLASTx homology to sialyltransferases, while ORF-3 (neuAhs) had BLASTx homology to CMP-sialic acid synthetases. These ORFs were amplified by PCR and cloned into the expression vector pCWOri+. Thin layer chromatography of the hsst-I gene product showed this sialyltransferase exhibited preference for sialylation of terminal N-acetyllactosamine (LacNAc, beta-Gal-[1,4]-beta-GlcNAc-R). However, Hsst-II preferentially sialylated lacto-N-biose (LNB, beta-Gal-[1,3]-beta-GlcNAc-R). In this study, phase variation of the terminal linkage in isolate 738 from a 3 linked galactose (LNB) to a 4 linked galactose (LacNac) was demonstrated. Such variation of a glycose linkage appears to be a novel mechanism of LOS phase variation. Furthermore, the ability of sialylated strain 738 LOS vs de-sialylated strain 738 LOS to induce Toll-like receptor 4 signaling was decreased by 28%, as determined by ELISA for Macrophage Inflammatory Protein-2. Therefore, sialylated LOS may aid H. somnus to avoid host innate immunity.Ph. D.
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Salame, Joumana. "EVALUATION OF TWO ORAL PROBIOTIC PRODUCTS FOR MICROBIAL VIABILITY AND IN VITRO INHIBITION OF SELECTED PERIODONTAL BACTERIAL PATHOGENS." Master's thesis, Temple University Libraries, 2011. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/147512.
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Oral BiologyM.S.
Objectives: One potential impact of oral probiotic products involves use of known bacterial antagonisms to alter the ecologic environment in periodontal pockets from one inhabited by pathogenic dental plaque microorganisms to one more favorable to colonization by non-pathogenic species (bacterial replacement). Until recently, the ability to introduce such beneficial effector bacteria into the oral cavity of periodontitis patients has been limited by the lack of specifically-formulated available commercial probiotic products. PerioBalance (Sunstar GUM), with two strains of the gram-positive, aerobic species Lactobacillus reuteri, and EvoraPlus (Oragenics), with freeze-dried strains of the gram-positive, aerobic species Streptococcus oralis, Streptococcus uberis, and Streptococcus rattus, are two recently-introduced commercial oral probiotic products proposed to have beneficial effects against periodontal disease. However, it is not known if the microbial species contained in these two oral probiotics are viable after the manufacturing process, and have the capability to exert inhibitory effects against putative periodontal bacterial pathogens when reconstituted in the oral cavity. Thus, the objective of the present study was to determine whether PerioBalance lactobacilli and EvoraPlus streptococci are viable upon product use, and possess in vitro inhibitory effects against fresh clinical strains of the putative periodontal bacterial pathogens, Tannerella forsythia and Prevotella intermedia/nigrescens, in the presence of anaerobic growth conditions. Methods: Commercial lots of PerioBalanceÒ and EvoraPlusÒ tablets were aseptically removed from the product packaging with sterile forceps, dissolved into Möller’s VMG I anaerobic dispersion solution, plated onto pre-reduced, enriched Brucella blood agar, and subjected to overnight anaerobic incubation at 35ºC in a culture cabinet containing 85% N2-10% H2-5% CO2, and to overnight aerobic incubation in a 5% CO2-95% air atmosphere. All culture plates were then visually examined under magnification for microbial colony growth. In vitro solid media competition assays were used to assess the in vitro inhibition capability of the two oral probiotics against T. forsythia and P. intermedia/nigrescens. Pioneer PerioBalance lactobacilli and EvoraPlus streptococci colonies were first grown on enriched Brucella blood agar media, followed by secondary spotting of T. forsythia and P. intermedia/nigrescens isolates immediately next to the established pioneer EvoraPlus and PerioBalanceÒ bacterial colonies such that they almost touched each other. After an additional overnight anaerobic incubation period, growth inhibition of the putative periodontal bacterial pathogens by the pioneer PerioBalance and EvoraPlus colonies was noted as the visual presence without magnification of a proximal zone of inhibition at the intersection of the pioneer colonies and the T. forsythia and P. intermedia/nigrescens colonies. Results: PerioBalance lactobacilli grew readily and in abundance in vitro on anerobically and anaerobically-incubated EBBA, with no other colony types or contaminating organisms. In contrast, EvoraPlus product samples purchased over-the-counter from drug stores in Maryland and Pennsylvania failed to exhibit any in vitro microbial growth under anaerobic and aerobic incubation conditions, with only EvoraPlus tablets obtained directly from the manufacturer yielding in vitro streptococcal growth. No in vitro inhibition was noted under anaerobic conditions of established PerioBalance lactobacilli and EvoraPlus streptococci pioneer colonies against subsequent growth of clinical isolates of T. forsythia and P. intermedia/nigrescens, with no zone of inhibition developing between their colonies and the immediately-adjacent established oral probiotic pioneer colonies. Conclusions: The two commercial oral probiotics evaluated varied considerably in the viability of their microbial constituents, with abundant growth of PerioBalance lactobacilli found in over-the-counter product material, and the lack of any EvoraPlus streptococci growth in product tablets obtained from sources other than directly from the manufacturer. Both oral probiotic products failed in vitro, in solid media competition assays, to inhibit growth of fresh clinical isolates the putative periodontal bacterial pathogens T. forsythia and P. intermedia/nigrescens under anaerobic growth conditions. These findings question the potential effectiveness of the two oral probiotic products to alter the subgingival ecology in periodontal pockets when anaerobic environmental conditions are present. Additional research is needed to assess the inhibitory potential of PerioBalance lactobacilli and EvoraPlus streptococci against additional isolates of subgingival bacterial species, and in circumstances where microaerophilic or aerobic environmental conditions are found.
Temple University--Theses
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Tansawat, Rossarin. "Microbial Growth Inhibition and Decomposition of Milk Mineral and Sodium Tripolyphosphate Added to Media or Fresh Ground Beef." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/304.
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Milk mineral (MM) is a type II antioxidant (metal chelator) that can bind iron and prevent iron catalysis of lipid oxidation. Thus, MM might have microbial growth inhibition effects on iron-dependent bacteria. Objective 1 was to evaluate effects of MM on growth of non-pathogenic iron-dependent bacterial strains (Listeria innocua, Eschericia coli, Pseudomonas fluorescens). MM (1.5 % w/v) did not significantly inhibit growth of Listeria and E. coli. However, growth of Pseudomonas fluorescens was consistently and significantly reduced by ~1 log colony forming units per ml (CFU/ml) with all levels of MM (0.5, 0.75, 1.5 % w/v). All levels of MM also had no growth inhibition effects against the mixed microflora of fresh ground beef during storage for up to 10 days at 2°C. In conclusion, MM had little or no effect to inhibit microbial growth. The strong affinity of MM to ionic iron inhibits lipid oxidation, but does not inhibit bacterial growth supported by other forms of iron (heme or amino acid + iron complexes).
Several studies report that MM has greater antioxidant effect than sodium tripolyphosphate (STP) in ground meats, especially at longer storage time. Objective 2 was to compare stability of MM and STP in ground beef patties by monitoring the decomposition to soluble orthophosphates (Pi). Patties (control) and patties with 0.75 % MM or 0.5 % STP were stored at 2 or 22°C for 0, 1, or 2 days. CFU/g and Pi were measured. As expected, CFU/g at 22°C was much higher than treatment at 2°C. Pi levels at 2°C were lower (P < 0.05) than at 22°C. At day 0, for both temperatures, patties formulated with MM had the highest Pi levels. However, after 2 days storage, samples with added STP had the highest level of Pi, followed by MM and control. Thus, decomposition as measured by release of Pi was significantly higher for STP than for MM added to beef patties. There was a significant positive correlation (0.77) between CFU/g and Pi during storage of beef patties for 2 days at 22°C. In conclusion, increased Pi during storage of beef patties was at least partially due to bacterial phosphatases. A third experiment was conducted to examine the stability of 0.75 % MM or 0.5 % STP added to growing cultures of Pseudomonas fluorescens at 2°C or 22°C for 0, 1, and 2 days. Neither MM nor STP was stable in autoclaved media (Pi increased significantly). The factors responsible for decomposition of MM or STP in autoclaved media remain to be determined.
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Löchner, Anne Christina [Verfasser], and Victor [Akademischer Betreuer] Sourjik. "Quorum sensing- and contact-dependent inhibition-based population control in synthetic microbial communities / Anne Christina Löchner ; Betreuer: Victor Sourjik." Marburg : Philipps-Universität Marburg, 2021. http://d-nb.info/1228535647/34.
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Savage, Matthew John. "Integrated Treatment Processes For Primary Wool Scouring Effluent." Thesis, University of Canterbury. Chemical and Process Engineering, 2003. http://hdl.handle.net/10092/1125.
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The increasing cost of effluent treatment in the wool scouring industry is rapidly becoming a determining factor in the viability of existing scouring operations and new installations alike. This thesis details the development of an integrated effluent treatment process capable of treating the worst polluted effluent from a wool scour "heavy flow-down", to the point where it can either be economically discharged to local trade waste sewer, or directly discharged to river or ocean outfall with minimal environmental impact. The existing proprietary chemical flocculation process, Sirolan CF™, was improved by the addition of a bio-flocculation stage and turbidity monitoring and control, and the product from this process fed to an aerobic biological treatment system based upon the traditional activated sludge process. The biological treatment process was found to remove up to 98% of the BOD5 loading from the pre-treated liquor with a hydraulic residence time of at least 50 hours being required in the aerobic digestion vessels. A residual biorefractory COD of approximately 3,600mg/L was identified which could not be removed by biological treatment. When operating continuously, the biological process was observed to metabolically neutralise the pH 3.0 - 4.5 feed from the chemical flocculation system to pH > 7.0 without the need for supplemental addition of neutralising agents such as sodium hydroxide. This in itself provides a significant economic incentive for implementation of the process. Kinetic analysis of the biological process carried out under controlled laboratory conditions using a Bioflo 3000 continuous fermentor showed that the bio-chemical process followed substrate inhibition kinetics. An appropriate kinetic model was identified to represent the behaviour of the substrate degradation system, and modified by inclusion of a pseudo toxic concentration to account for the effect of pH inhibition upon the biological growth rate. The process was verified both at pilot plant scale and at demonstration plant scale at an operational wool scour. The demonstration plant was of sufficient size to handle the full heavy effluent flow-down from a small wool scour. At the time of publishing three full-scale effluent treatment systems based on this research had been sold to both domestic and international clients of ADM Group Ltd. who funded the research.
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Bailey, Andrea J. 1952. "Measurement of Feedback Inhibition In Vivo and Selection of ATCase Feedback Altered Mutants in Salmonella typhimurium." Thesis, University of North Texas, 1989. https://digital.library.unt.edu/ark:/67531/metadc330749/.
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Aspartate transcarbamoylase (ATCase; encoded by pyrBI genes) is one of the most studied regulatory enzymes in bacteria. It is feedback inhibited by cytidine triphosphate (CTP) and activated by adenosine triphosphate (ATP). Much is known about the catalytic site of the enzyme, not nearly as much about the regulatory site, to which CTP binds. Until now a positive selection for feedback-modified mutants was not available. The selection we have developed involves the use of a pyrA deletion in S. typhimurium. This strain lacks carbamoylphosphate and requires both a pyrimidine and arginine for growth. In this strain citrulline is used to satisfy the pyrimidine and arginine requirements. The minimal flow through the pyrimidine pathway from the citrulline-produced carbamoylphosphate is exquisitely sensitive to feedback control of ATCase by CTP. By elevating the CTP pool, via exogenous cytidine, in a strain that also contains a cytidine deaminase mutant (cdd) growth can be stopped completely, indicating 100% inhibition. It was therefore possible to measure in vivo feedback inhibition of ATCase among the citrulline users and to isolate a family of ATCase regulatory mutants with either modified or no response to effectors.
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Bueno, Pedro Vinicius de Assis. "Complexos híbridos de polieletrólitos e magnetita para liberação controlada de amoxicilina." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-24092018-145617/.
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Novos sistemas biocompatíveis para aplicações biotecnológicas são relevantes não só do ponto de vista tecnológico, mas também para avanços científicos. A presente dissertação visou à criação e caracterização de filmes finos (espessura de até 100 nm) ou micrométricos (espessura de 50 µm a 100 µm) formados por goma xantana (GXT), poli(cloreto de dimetil dialil amônio), (PDDA), albumina bovina sérica (BSA), e nanopartículas de magnetita (NPM). A incorporação de amoxicilina (Amox), um antibiótico amplamente utilizado contra muitas infecções, nos filmes foi realizada durante a formação dos sistemas. Os filmes finos foram caracterizados através de elipsometria e microscopia de força atômica. Em solução, as interações favoráveis entre o Amox e a BSA foram evidenciadas por mudanças substanciais na estrutura secundária da BSA, como revelado pelo dicroísmo circular. Os filmes micrométricos (patches) de GXT e GXT/NPM/BSA foram imersos em Amox 2 g/L, levando a incorporação de 10 ± 3 e 17 ± 4 µg/cm³ de Amox, respectivamente. Sua caracterização compreendeu espectroscopia vibracional no infravermelho por transformada de Fourier no modo de refletância total atenuada (FTIR-ATR), microscopia eletrônica de varredura (MEV), medidas de sorção e espectrometria de emissão óptica com plasma indutivamente acoplado (ICP-OES). A incorporação de 0,2% em massa de Fe3O4 nos \"patches\" e sua exposição a um campo magnético externo, viabilizou a liberação total in vitro de Amox, em pH 5,5 e em 0,02 mol/L de NaCl, seguindo o comportamento quasi-Fickiano. A difusão da Amox dos \"patches\" de GXT/NPM/BSA em ágar contendo Staphylococcus aureus e Escherichia coli, levou halos de inibição consideráveis. A inibição do crescimento de E. coli foi particularmente eficiente sob efeito de campo magnético externo.New biocompatible systems for biotech applications are relevant not only from a technological point of view, but also for scientific advances. The present project aimed at the creation and characterization of thin films (thickness up to 100 nm) or micrometric patches (thickness of 50 µm to 100 µm) formed by the deposition of xanthan gum (GXT), poly (dimethyl diallyl ammonium chloride) (PDDA), bovine serum albumin (BSA), and magnetite nanoparticles (NPM). The incorporation of amoxicillin (Amox), a widely used antibiotic against many infections, in the films was performed during the formation of the systems. Thin films were characterized by means of ellipsometry and atomic force microscopy. In solution, favorable interactions between Amox and BSA were evidenced by substantial changes in the secondary structure of BSA, as revealed by circular dichroism spectra. Patches of GXT and GXT/NPM/BSA were immersed into Amox solution at 2 g/L, leading to the Amox incorporation of 10 ± 3 and 17 ± 4 µg/cm3, respectively. The patches characterization included Fourier Transform Infrared vibration spectroscopy in the attenuated total reflectance mode (FTIR-ATR), scanning electron microscopy (MEV), sorption measurements and inductively coupled plasma optical emission spectrometry (ICP-OES). The incorporation of 0.2 wt% of Fe3O4 in the patches and their exposure to an external magnetic field, allowed the total in vitro release of Amox, at pH 5.5 and 0.02 mol/L NaCl, following the behavior quasi-Fickian. Amox diffusion from GXT/NPM/BSA patches in agar containing Staphylococcus aureus and Escherichia coli led to a considerable zone of inhibition. Inhibition of E. coli growth was particularly efficient under the effect of external magnetic field.
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Rebello, Fabiane Ramos. "Otimização e verificação dos métodos microbiológicos empregados no controle de qualidade de medicamentos de uso oral." reponame:Repositório Institucional da FIOCRUZ, 2015. https://www.arca.fiocruz.br/handle/icict/13007.
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Previous issue date: 2015Fundação Oswaldo Cruz. Instituto de Tecnologia em Fármacos/Farmanguinhos. Rio de Janeiro, RJ, Brasil.
Atualmente é notório o crescimento da Gestão da Qualidade e, com esta, desenvolvem-se também as Boas Práticas de Fabricação e Controle, que são ferramentas que auxiliam na obtenção de produtos de qualidade. Ao falar de qualidade na indústria farmacêutica, fala-se, sobretudo da qualidade físico-química e microbiológica tanto das matérias-primas empregadas na fabricação como do produto terminado obtido após as diversas etapas produtivas. Com objetivo de alcançar esta qualidade este projeto buscou verificar as metodologias empregadas no dia a dia da Divisão de Controle de Especificação do Laboratório Farmacêutico da Marinha (LFM). As técnicas empregadas no controle microbiológico, em sua maioria, são as mesmas, consistindo na realização do ensaio limite (contagem de micro-organismos) e na pesquisa e identificação de patógenos. No entanto deve-se verificar se o produto analisado não afeta o crescimento microbiano, inibindo-o e fazendo com que se tenha resultados falso-negativos, o que acarretaria em desvios da qualidade podendo levar a danos para a saúde do usuário e prejuízos para a imagem da Instituição. Elegeram-se as seguintes formulações, todas de uso oral, para serem avaliadas: aciclovir 200 mg comprimidos, isoniazida 100 mg comprimidos, pirazinamida 500 mg comprimidos, ofloxacino 400 mg comprimidos, pirazinamida suspensão 3%, bromexina xarope, prednisona 5 mg comprimidos e complexo vitamínico e minerais comprimidos. Estas formulações foram avaliadas frente às cepas de referência, conforme procedimentos preconizados pela Farmacopeia Brasileira 5ª Ed. Durante o ensaio verificou-se que todas as formulações, exceto o aciclovir e a pirazinamida suspensão, inibiram o crescimento das cepas testadas. Foram testados métodos de neutralização da atividade inibitória do crescimento microbiano, tendo sido selecionados os seguintes procedimentos: diluição para as formulações de isoniazida 100 mg, prednisona 5 mg e complexo vitamínico, uso de neutralizante, polissorbato 80, para bromexina xarope e filtração por membrana para pirazinamida 500 mg comprimidos, logrando-se êxito para o ensaio do limite. Somente para o ofloxacino não foi possível recuperar os micro-organismos e no caso da pirazinamida comprimidos, a mesma não foi susceptível à pesquisa de Escherichia coli, nas condições preconizadas pela Farmacopeia Brasileira 5ª Ed. O presente trabalho identificou que das oito formulações testadas, seis inibem o crescimento microbiano e, portanto interferem na análise. Após adequações, os métodos responderam aos testes e foram desta forma considerados validados, podendo ser utilizados de forma segura na rotina do laboratório.
Nowadays it is remarkable the development of the Quality Management, together with it the Good Manufacturing Practices and Control, which are tools that help to afford products with high quality. Concerning to quality issues in the Pharmaceutical Industry, the main objective is to achieve high physical-chemical and microbiological quality of the raw materials used for manufacturing, as well of the final product after the several processing steps. Aiming to succeed in attaining this quality parameter, this project has attempted to verify the methodologies daily employed by the Specification Control Division of Brazilian Navy Pharmacautical Laboratory (LFM). The techniques employed for the microbiological quality control are usually the same, and consist of performing the limit assay (microorganism counting) and the search and identification of pathogens. Nevertheless, it must be checked if the product under analysis does not affect the microbial growth, causing an inhibition and leading to false-negative results, which might drive to quality deviance, ultimately harming the final user and bringing damage to the institution image. In this project, the following oral formulations have been selected to be evaluated: aciclovir 200 mg tablets, isoniazid 100 mg tablets, pyrazinamide 500mg tablets, ofloxacin 400 mg tablets, pyrazinamide 3% suspension, bromexine syrup, prednisone 5 mg tablets and tablets containing vitamin complex and minerals. These formulations have been evaluated against the growth of reference strains, in accordance to the procedures described in the Brazilian Pharmacopeia 5th Edition. During the assay, it has been found all formulations, exemption given to aciclovir and pyrazinamide suspension, inhibited the growth of the assayed strains. Methods for neutralizing the microbial growth inhibition activity have been assessed and the selected procedures were: diluition for isoniazid 100mg, prednisone 5 mg and vitamin complex; use of the neutralizer polysorbate 80 for bromexine syrup; and membrane filtration for pyrazinamide 500 mg tablets, which allowed the recovery of all microorganisms. Only for ofloxacin it was not possible to recover the microorganisms and for pyrazinamide tablets, the formulation was not susceptible to the Escherichia coli assay, pursuant to the Brazilian Pharmacopeia 5th Edition. The present study has identified that six out of the eight assayed formulations have inhibited microbial growth, therefore interfering in the analysis outcome . After adjustments, the methods have trustworthy worked and were thus considered validated, and now can be applied safely in the laboratory's routine.
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Moreno, Lilliana I. "The Effect of Sample and Sample Matrix on DNA Processing: Mechanisms for the Detection and Management of Inhibition in Forensic Samples." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/1764.
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The presence of inhibitory substances in biological forensic samples has, and continues to affect the quality of the data generated following DNA typing processes. Although the chemistries used during the procedures have been enhanced to mitigate the effects of these deleterious compounds, some challenges remain. Inhibitors can be components of the samples, the substrate where samples were deposited or chemical(s) associated to the DNA purification step. Therefore, a thorough understanding of the extraction processes and their ability to handle the various types of inhibitory substances can help define the best analytical processing for any given sample. A series of experiments were conducted to establish the inhibition tolerance of quantification and amplification kits using common inhibitory substances in order to determine if current laboratory practices are optimal for identifying potential problems associated with inhibition. DART mass spectrometry was used to determine the amount of inhibitor carryover after sample purification, its correlation to the initial inhibitor input in the sample and the overall effect in the results. Finally, a novel alternative at gathering investigative leads from samples that would otherwise be ineffective for DNA typing due to the large amounts of inhibitory substances and/or environmental degradation was tested. This included generating data associated with microbial peak signatures to identify locations of clandestine human graves. Results demonstrate that the current methods for assessing inhibition are not necessarily accurate, as samples that appear inhibited in the quantification process can yield full DNA profiles, while those that do not indicate inhibition may suffer from lowered amplification efficiency or PCR artifacts. The extraction methods tested were able to remove >90% of the inhibitors from all samples with the exception of phenol, which was present in variable amounts whenever the organic extraction approach was utilized. Although the results attained suggested that most inhibitors produce minimal effect on downstream applications, analysts should practice caution when selecting the best extraction method for particular samples, as casework DNA samples are often present in small quantities and can contain an overwhelming amount of inhibitory substances.
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Hibler, David A. "Development of a Two-Stage Computational Modeling Method for Drinking Water Microbial Ecology Effects on Legionella pneumophila Growth." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595509673321504.
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Mody, Shreena Himanshu. "The Antimicrobial Properties of Honey and Their Effect on Pathogenic Bacteria." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7042.
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Honey has been used to heal wounds since ancient times. There are many references in ancient literature that cite honey for its medicinal uses. It is used as an alternative agent to cure infections of wounds, burns, ulcers etc. Researchers have shown some of the antimicrobial properties of honey when used as an ointment. When applied to an affected area, it helps to promote the growth of healthy tissue. One of the factors on which the quality of the honey depends, is its geographical origin. Based on the location, honey types can vary as much as 100-fold from each other in color, aroma, viscosity, and antimicrobial properties. The important components in honey that play an essential part in healing wounds and contributing to the antimicrobial properties are enzymes. Their presence allows honey to kill various types of pathogenic bacteria, viruses, fungi etc. A higher antimicrobial effect is seen in monofloral honey (when a single plant species is the source of nectar), which is often more potent than other types of honey in terms of antibacterial activity. Resistance of pathogens to these antimicrobial actions has never been shown, which makes honey a more promising source of antimicrobial research. Presently, infections of burns and wounds are very challenging to treat, especially when they are caused by antibiotic-resistant bacteria. The purpose of this study was to examine the antimicrobial properties of honey from Utah and other locales, and to identify promising antimicrobial activities that could be useful in treating infections caused by resistant bacteria.
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Wietek, Jonas. "Anion Conducting Channelrhodopsins." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19325.
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Seit mehr als 10 Jahren kann biologische Aktivität durch eine Vielzahl photosensorischer Proteine beeinflusst werden. In diesem als Optogenetik bezeichneten Forschungsgebiet, werden Kationen leitende Kanalrhodopsine (CCRs) als lichtinduzierte neuronale Aktivatoren eingesetzt. Diese Arbeit soll zur Vervollständigung von optogenetischen Werkzeugen durch die Entwicklung Anionen leitender Kanalrhodopsine (ACRs) dienen, um die bestehenden Nachteile mikrobieller lichtgetriebener Ionenpumpen zu überwinden, die bislang zur neuronale Inhibition genutzt wurden.
Der Austausch von E90 in C. reinhardtii Kanalrhodopsin 2 (CrChR2) durch positiv geladene Aminosäuren führte zu Entwicklung Chlorid leitender ChRs (ChloCs), die jedoch eine Restkationen-permeabilität aufwiesen. Durch Substitution zweier weiterer negativen Ladungen innerhalb des Ionenpermeationsweges, konnte die Kationenleitung vollständig aufgehoben werden.
Parallel wurde durch A. Berndt et al. ein inhibitorisches C1C2 (iC1C2), basierend auf der CrChR1/2 Chimäre entwickelt. Wie auch bei den ChloCs, zeigte iC1C2 verbesserungswürdige biophysikalische Eigenschaften. Mutagenesestudien des Ionenpermeationsweges führten zur Entwicklung der verbesserten Nachfolgervariante iC++.
Um ausgehend von weiteren CCRs neuartige ACRs zu entwickeln (eACRs), wurden die zuvor angewandten Mutagenesestrategien auf weitere CCRs übertragen. Zwei neue eACRs, Phobos und Aurora, mit jeweils blau- und rotverschobenen Aktionsspektrum konnten generiert werden. Bistabile eACRs wurden erzeugt, die ein lichtgesteuertes Schalten zwischen offenen und geschlossenen Zuständen ermöglichen.
Schlussendlich wurde ein natürlich vorkommendes ACR (nACR) aus Proteomonas sulcata (PsACR1) identifiziert und charakterisiert. Die Maximalaktivität von PsACR1 zählt mit 540 nm zu den am stärksten rotverschobenen unter den nACRs. Elektrophysiologische und spektroskopische Untersuchungen ergaben, dass sich der Photozyklus von PsACR1 signifikant von jenen der CCRs unterscheidet.For more than 10 years, photosensory proteins have developed as powerful tools to manipulate biological activity. In this research field termed optogenetics, cation-conducting channelrhodopsins (CCRs) mainly are utilized as light-induced neural activators. This study aimed at a complementation of the optogenetic tool box by engineering anion-conducting channelrhodopsins (ACRs) to overcome the existing drawbacks of microbial light-driven ion pumps utilized for neural inhibition so far. Replacement of E90 in the cation-conducting C. reinhardtii channelrhodopsin 2 (CrChR2) with positively charged residues reversed the ion selectivity and yielded chloride-conducting ChRs (ChloCs). Applied in neuronal cell culture, ChloCs showed residual cation permeability occasionally leading to excitation instead of the desired inhibition. Further charge elimination within the ion permeation pathway completely abolished cation conduction. In parallel, an inhibitory C1C2 (iC1C2) was developed by A. Berndt et al. based on a CrChR1/2 chimera. Though, iC1C2 displayed unsatisfactory biophysical properties as well. Further mutational modifications of the ion permeation pathway led to the development of the improved successor variant iC++. A systematic transfer of both conversion strategies to other CCRs was conducted to create engineered ACRs (eACRs) with distinct biophysical properties. Two novel eACRs, Phobos and Aurora, with blue- and red-shifted action were obtained. Additionally, step-function mutations greatly enhanced the operational light sensitivity and enabled temporally precise toggling between open and closed states using two different light colors. Finally, a natural ACR (nACR) originating from Proteomonas sulcata (PsACR1) was identified and characterized. With a maximum activation at 540 nm it is one of most red-shifted nACRs. Single turnover electrophysiological measurements and spectroscopic investigations revealed an unusual photocycle compared to that of CCRs.
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Hastings, Cody M. "Determination of the effects that a previously uncharacterized secreted product from Klebsiella pneumoniae has on Citrobacter freundii and Enterobacter cloacae biofilms." Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/honors/419.
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More so than ever, Multiple Drug Resistant (MDR) bacteria are on the rise due to overuse of antibiotics along with natural selection for adaptations that enhance drug-resistant properties. One particular bacterial family, Enterobacteriaceae, has been problematic, exhibiting several bacterial members that have developed a precipitous resistance to modern antibiotics and are also primary causative agents of nosocomial, or hospital acquired, infections. Citrobacter freundii (CF) and Enterobacter cloacae (ECL) are two species of the Enterobacteriaceae family causing significant medical concern due to their role in producing numerous opportunistic infections such as bacteremia, lower respiratory tract infections, urinary tract infections, and endocarditis. Adding to the difficulty of this situation is the ability of bacteria to produce biofilms. These biofilms are communities of bacteria that exhibit increased resistance to antibiotic treatment and eradication. Previous work in the laboratory of Dr. Fox at ETSU has identified an uncharacterized product secreted by Klebsiella pneumoniae (KP), another member of the Enterobacteriaceae family, which appears to have inhibitory effects toward CF and ECL. The current study was designed to characterize the effects this secreted product has on CF and ECL biofilms. Through a high throughput microtiter plate assay, the effects of this secreted product were examined on CF and ECL phases of biofilm attachment and maturation. Based on our findings, we have concluded that this secreted product can be categorized as a possible bacteriostatic agent against biofilm cell density, biofilm mass, and cell viability for both biofilm phases of attachment and maturation.
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Marsh, Lorraine Hazel. "Inhibiting bacterial adhesion to biological surfaces." Thesis, University of Portsmouth, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369437.
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Reveneau, Carine. "Dietary source and availibility [i.e. availability] of fatty acids to manipulate ruminal protozoa, metabolism of fat, and milk fatty acid profile in lactating dairy cows." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1204659455.
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Gao, Geng. "Fragment Library Screening to Discover Selective Inhibitors of a Key Microbial Enzyme." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1290184812.
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Griffin, Allian Sophia. "Corrosion in New Construction:Elevated Copper, Effects of Orthophosphate Inhibitors, and Flux Initiated Microbial Growth." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/76951.
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It is generally acknowledged that a variety of problems affecting aesthetics, health, and corrosivity of potable water can arise during installation of building plumbing systems. These include 'blue water', microbial infestation, and rapid loss of disinfectant residual, among other things. Frequently cited causes of the problems include metallic fines left in the plumbing lines from deburring, cutting and product fabrication; solder flux residuals (water soluble and petroleum based flux); and solvents for CPVC. Mechanistically, some materials such as flux contain high chloride, high ammonia and cause low pH, which can increase the corrosivity of water held in the lines. Indirect effects are also suspected to be important. For example, ammonia from flux and organic carbon from flux or PVC solvents can spur microbial growth, which in turn can reduce pH or otherwise increase corrosivity. Recent work has also demonstrated that problems with lead leaching to water from brass in modern plumbing can actually be worse in PVC/plastic than in copper systems, if certain types of microbes such as nitrifiers proliferate and drop pH. Some of the problems initiated by construction practices can persist indefinitely, causing higher levels of lead and copper in water, or longer term, contributing to failures of the plumbing system.
Blue water from high copper concentrations is a confounding problem that continues to arise in some locales of the United States. One public elementary school in Miami Dade County is experiencing blue water issues as manifested by blue ice cubes and sink staining. In addition to the aesthetic problems, copper levels are above the EPA's Copper Action Level of 1.3 ppm. Bottled water has been substituted for tap water consumption, which has created a financial burden. The pH of the school's water ranges from 7.15 - 7.5 and the school itself is located 1 ½ miles off the main distribution line resulting in a very low chlorine residual of between 0.06 mg/L Cl2 and 0.18 mg/L Cl2. On site water was shipped to Virginia Tech from Miami to be used in this study. Preliminary testing showed that an increase in the pH of the water would decrease copper leaching. Several pH's were tested which revealed that increasing the pH of the water to 8.5 would drop copper below 1.3 mg/L. When these recommendations were implemented at the school, the high alkalinity and calcium rich water caused calcite scales to form which clogged the chemical feed nozzles. Further bench scale testing indicated that adding 2 mg/L orthophosphate corrosion inhibitor would effectively decrease copper to a level that would comply with the EPA's Copper Action Limit.
Orthophosphate corrosion inhibitors are used by utilities to limit lead and copper corrosion from consumer's plumbing. An evaluation comparing the effects of both 100% orthophosphate inhibitor and orthophosphate/polyphosphate inhibitor blends was performed to study the effects they have on galvanic corrosion, metallic corrosion, microbial growth and the decay of chloramine disinfectant. On site water was sent to Virginia Tech from UNC for use in this bench scale study. The results from this study indicated that 100% orthophosphate inhibitor was the most effective corrosion inhibitor at decreasing metallic corrosion.
It has long been known that microbial activity can have significant effects on water quality. This study evaluated nitrifying and heterotrophic bacterial growth in water systems containing copper pipes, a common plumbing product, and flux which is used in soldering copper pipes together in new construction. There are several types of commercially available fluxes which are often used when soldering new pipes together. Flux ingredients vary and can include extremely high concentrations of ammonia, zinc, chloride, tin, copper and TOC. Flux containing high amounts of ammonia can be detrimental to water quality because it can accelerate the occurrence of nitrification, thus creating a cascading set of problems including, but not limited to, pH decrease and copper corrosion. The results from this case study indicated that flushing a pipe system can effectively decrease the high concentrations of flux present in a new construction system; however, high levels of ammonia from flux can create an environment in which nitrifiers may proliferate within the system.
Many water utilities in the United States are switching disinfection type from chlorine to chloramine due to the increased stability, longer residual time, and overall safety benefits of chloramine. Although chloramines have been found to be a desirable means for disinfection, chloramine decay is an issue of great concern because if the chloramine residual decays, it can leave a water system unprotected against microbial infestation. A preliminary examination of this issue was performed in a laboratory setting to evaluate the many components that effect the stability of chloramine decay, including alkalinity, phosphate, temperature, and various pipe materials. The results from this experiment revealed that temperature increase, pH increase, and aged tygon tubing all accelerated the rate of chloramine decay.Master of Science
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Romero, Rueda Tamara. "Evaluation of false positive results in microbial inhibitor tests for screening antibiotics in goat milk." Doctoral thesis, Universitat Politècnica de València, 2015. http://hdl.handle.net/10251/48552.
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Goat milk is primarily destined for the production of fermented products, in particular
cheese. Therefore, the control of antibiotic residues in milk is of great importance, since
these could have negative repercussions on technological properties of the milk as well
as on the health of consumers.
In milk quality control programs, microbial inhibitor tests are widely applied to detect
antibiotics during the screening stage. However, tests are non-specific and may be
affected by substances other than antimicrobials which could inhibit the growth of the
test micro-organism, causing false positive results.
The aim of this thesis was to evaluate the interference, related to the presence of
different contaminants in goat milk, on the response of microbial inhibitor tests
commonly used in Spain to detect antibiotics (BRT MRL, Delvotest SP-NT MCS and
Eclipse 100 tests). The influence of the physicochemical characteristics of goat milk on
the false positive outcomes in microbial screening tests was also investigated.
The suitability of microbial inhibitor tests for screening antibiotics in colostrum
secretions was studied by analysing antibiotic-free colostrum and milk samples from
forty-three Murciano-Granadina goats, collected every 12 hours during the first week
post-partum. Microbial inhibitor tests were not suitable for the analysis of goat
colostrum because they presented a high percentage of doubtful and positive results
(up 37.2% in the 36 hours after partum).
To evaluate the effect of caprine colostrum on the microbial test response,
antimicrobial-free goat milk spiked with different concentrations of colostrum was
analysed to calculate the inhibitory concentrations producing 5% of positive results.
The highest interferences were obtained for the addition of colostrum from 12 to 24
hours post-partum and the colostrum concentrations producing 5% positive results
were between 5.1 and 34.6%. The BRT MRL was the test the most affected.
In another study, the interference of detergents and disinfectants used for the cleaning
of milking equipment and milk storage tanks of dairy farms was investigated.
Antimicrobial-free goat milk was spiked with eight concentrations of different cleaning
products (5 acid, 5 alkaline, 5 domestic washing-up liquids, and 1 disinfectant) and
analysed using microbial screening tests. The presence of acid detergent and
disinfectant based on sodium hypochlorite in goat milk did not affect the microbial test
response. However, alkaline detergents at concentrations ≥ 1 ml/l could lead to false
positive results in microbial inhibitor tests (up to 16.7%) and from 4 ml/l on 100%
positive results were obtained. Regarding the products used for home use, and those
used on farms and small size dairies, washing-up liquid containing sodium laureth
sulphate and ethanol had the greatest effects on microbial inhibitor tests, even starting
from a relatively low concentration (1 ml/l). On the other hand, the presence of a
relatively low concentration of detergents in goat milk (0.5 ml/l) slightly modified the
detection capability of the microbial inhibitor tests for amoxicillin, ampicillin,
benzylpenicillin, and cloxacillin, although the detection of these drugs at MRL (safe
level) was not compromised.
Antiparasitic agent residues in goat milk could be another possible cause of false
positive results in microbial screening tests. An in vitro study to evaluate the effect of
seven parasiticides commonly used in dairy goats was carried out. Further two studies,
where albendazole and ivermectin were applied to two groups of dairy goats in
lactation were performed. It should be noted that the parasiticide ivermectin is banned
for the treatment of animals producing milk for human consumption, although its
inclusion in this study was considered interesting to understand the potential effect of
their residues in milk, in the event the practice was performed illegally.
In the in vitro study, raw antibiotic-free milk from goats was spiked individually with eight
different concentrations of albendazole, closantel, diclazuril, febendazole, levamisole,
diazinon, and ivermectin. The microbial inhibitor test results showed a great variability
according to the test and the drug under study. Of the tests considered, the BRT MRL
test was the most sensitive to antiparasitic agents, with the lowest concentrations of
antiparasitic agent causing 5, 10, and 50% of positive results. Generally, closantel and
diazinon were the antiparasitic agents that produced higher interferences in all tests,
since low concentrations already resulted in positive results, while only higher
concentrations of diclazuril and ivermectin showed an inhibitory effect.
To evaluate the effect of albendazole residues on the microbial inhibitor test response,
eighteen healthy Murciano-Granadina goats in mid-lactation were treated with a single
oral administration of the commercially available albendazole registered for dairy sheep
(7.5 mg/kg b.w. of active compound) with a withdrawal period of 4 days for milk
production in ovine. Albendazole and its metabolite residues in goat milk after under
cascade treatment were not detected above MRL from the third day post-administration.
However, a high occurrence of non-compliant results was obtained for the BRT MRL test
during the first six days after treatment, suggesting that factors related to the
albendazole application other than the drug concentration are able to affect the microbial
inhibitor test response in some cases.
Regarding the ivermectin study, twenty-eight Murciano-Granadina goats infested with
Sarcoptes scabiei var. caprae were treated with a subcutaneous injection of ivermectin
(200 μg/kg b.w.), with a second dose applied seven days after the first treatment. Drug
residues in goat milk were recorded during the first fifteen days of the experiment with
concentrations ranging from 8.13 to 24.25 ng/ml. In addition, all the microbial screening
tests seem to be affected by the ivermectin treatment, with BRT MRL the most affected
(20%) compared with Delvotest SP-NT MCS and Eclipse 100 (6.6 and 5.7%,
respectively). These positive results cannot be associated with the ivermectin
concentration in goat milk, as the concentrations measured were lower than the
inhibitory concentrations as reported in a previous in vitro study for these microbial
tests. Thus, as suggested by some authors, interferences could be related to changes
or alterations caused by the application of the parasiticide agent or by the parasitic
disease itself, which could affect the immune response of the animals favouring the
presence of inhibitory substances in milk.
The study of the effect of the goat milk composition on the specificity (rate of false
positive results) of microbial inhibitor tests for screening antibiotics was also
considered. Thus, individual goat milk samples (n=200) were analysed by microbial
inhibitor tests using both visual and instrumental classification of the test results. The
highest specificity values were obtained for the instrumental interpretation of the test
results (94-99% vs 90-96%) due to the occurrence of samples with intermediate
colorations (green-yellow, yellow-blue) making the visual classification more difficult
and subjective. A relation was found between positive results in BRT MRL and Eclipse
100 tests and an elevated fat content in the goat milk. Positive outcomes in Eclipse 100
were associated with the butyric acid concentration in the milk. Further, the Delvotest
SP-NT MCS test response was affected by elevated pH values, high lactoferrrin and
myristoleic acid concentrations in the goat milk. This percentage of positive results
could be minimized by a pre-treatment prior to microbial inhibitor test analysis, such as
fat removal by centrifugation (3,100 g for 10 min at 4 ºC) and/or heating (80 ºC for 10
min).
Undoubtedly, improvements on the specificity of the microbial inhibitor tests for
screening antibiotics in goat milk are desirable to avoid the destruction of milk
compliant for human due to the occurrence of false positive results. The related
financial losses affect farmers and dairies. However, it should be noted that the
presence of contaminants in goat milk could be avoided by applying good farming
practices designed to ensure that milk is obtained from healthy animals under proper
hygienic conditions so ensuring the food safety of goat milk and related dairy products.Romero Rueda, T. (2015). Evaluation of false positive results in microbial inhibitor tests for screening antibiotics in goat milk [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48552
TESIS
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Sima, Hong. "Selective inhibition of acidophilic thiobacilli for application of controlling microbially-induced corrosion in concrete sewers." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185991.
Full textAbstract:
Recent interest in Thiobacillus thiooxidans has arisen from its central role in rapid, costly corrosion of concrete sewers. This study focuses on biochemical and ultrastructural responses of the intact cells and isolated carboxysomes, the polyhedral inclusions and CO₂ fixation sites, of the chemolithoautotroph to chemical inhibitors. Inhibition experiments were conducted in pure, batch cultures, grown in a basal salts medium using elemental sulfur as the energy source. D-ribulose 1,5-bisphosphate carboxylase (RuBPCase), the key enzyme of CO2 assimilation in T. thiooxidans, was chosen as the target for chemical inhibition. Observations were based on multiple metabolic measurements of cell growth, acid production, O2 respiration, CO₂ assimilation, intracellular ATP, and subcellular ultrastructure. Weak organic acids proved capable of inhibiting thiobacillus metabolism. Bacterial sensitivity was strongly dependent upon culture pH relative to the respective pKₐ values. Pyruvate and oxaloacetate were strong growth inhibitors. 2-c-carboxy-Darabinitol 1,5-bisphosphate (CABP) and hydroxylamine blocked in vivo CO2 assimilation and growth of T. thiooxidans without affecting on bacterial respiration. Evidence that the primary site of the selective inhibition lies on the biosynthetic side was supported by measurements of intracellular ATP and transmission electron microscopy (TEM). Dimethyl sulfoxide (DMSO) substantially promoted CABP inhibition of CO2 fixation by increasing cell membrane permeability. Carboxysomes were observed in intact cells of T. thiooxidans and characterized in the isolated form. Cell partitioning experiments showed that RuBPCase is sequestered and concentrated in these polyhedral inclusions. TEM observations were performed in conjunction with inhibitor studies. Treatment with the specific inhibitors, such as CABP and hydroxylamine, more than doubled the numbers of carboxysomes per cell without altering the shape and structure of the inclusion bodies, while effectively blocking both in vivo and in vitro CO₂ fixation. In contrast, non-specific inhibitors (cyanide, etc.) caused general intracellular disorder in thiobacilli and structural damage among isolated carboxy somes at concentrations that inhibited metabolic activities. Results suggest that by targeting critical, unique biochemical features of the acidophilic thiobacilli, it is possible to selectively inhibit these organisms, thereby mitigating the severity of sewer corrosion, without affecting general sewer biota or endangering down-stream biological wastewater treatment operations.
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Rath, Sebastian. "Anti-angiogenic effects of cytotoxic, microbial derived compounds - Evaluation of the tubulin inhibitor pretubulysin and its derivatives and characterization of the v-ATPase inhibitor concanamycin A." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-149868.
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Dykstra, Natalie. "The investigation of microbial-intestinal epithelial cell interactions in the gut and their effects on inhibitor of apoptotic proteins (IAPs)." Thesis, University of Ottawa (Canada), 2008. http://hdl.handle.net/10393/27978.
Full textAbstract:
Probiotic bacteria such as Lactobacillus plantarum strain 299v (Lp299v) have been shown to upregulate facets of innate immunity. This study assessed whether Lp299v prevents apoptosis in intestinal epithelial cells (IECs) when faced with cytokine challenge. Both in vitro and in vivo systems were exposed for a pre-determined time to Lp299v or strain Lpadh---a non-adherent derivative of Lp299v. HT-29 cells were then challenged with cytokine mixture (TNF-alpha, IFN-gamma, and IL-1a) to imitate conditions of inflammation. To assess for apoptosis, we evaluated both TUNEL analysis and caspase activity assays. Results of the assays indicate a marked decrease in apoptosis in samples treated with Lp299v. The adherent negative Lpadh-strain showed similar but less pronounced prevention of cytokine-induced apoptosis. IAPs were assessed both in vitro and in vivo and HIAP1 and HIAP2 were determined to be involved in this process. This is consistent with NF-kB activation by Lp299v. Probiotics may confer exogenous effects on IECs to elaborate protective mechanisms and alter cell homeostasis through alteration of caspase-dependent apoptosis.
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Niu, Chen. "The Role of Autoinducer-2 in Escherichia coli Biofilm Formation and the Discovery of a Plant-derived Quorum Sensing Inhibitor." Digital Archive @ GSU, 2006. http://digitalarchive.gsu.edu/biology_diss/5.
Full textAbstract:
The objectives of this work are: 1) to determine whether plant essential oil components influence the ability of Escherichia coli and several Pseudomonas species to form biofilms, and inhibit bacterial quorum sensing; 2) to understand the role of autoinducer-2 (AI-2) in biofilm formation by E. coli W3110. The biofilm formation assays determined that cinnamon, cassia and citronella oils differentially affected growth-normalized biofilm formation by E. coli. Cinnamaldehyde (CA) also inhibited the swimming motility of E. coli. Subinhibitory concentrations of CA were effective at inhibiting two types of acyl homoserine lactone (HSL) mediated quorum sensing (QS), and also AI-2 mediated QS. Because CA is widely used in the food and flavor industries, its potential to affect bacterial QS regulated processes should be recognized. The role of AI-2 mediated QS expression in physiology of E. coli W3110 was pleiotropic, including carbon utilization, fimbriae production, and the biofilm development. Overall, the research presented in this dissertation supported the concept that QS, biofilm formation, and cell adhesion may be broadly correlated. The anti-biofilm and anti-QS capability of CA implies that plant essential oil components might be promising for preventing the formation of detrimental biofilms.
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Rath, Sebastian [Verfasser], and Stefan [Akademischer Betreuer] Zahler. "Anti-angiogenic effects of cytotoxic, microbial derived compounds - Evaluation of the tubulin inhibitor pretubulysin and its derivatives and characterization of the v-ATPase inhibitor concanamycin A / Sebastian Rath. Betreuer: Stefan Zahler." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2012. http://d-nb.info/1027669530/34.
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Nasr, Mostafa M. "Mitigation of Microbially Induced Concrete Corrosion in Wastewater Infrastructure using Surface Treatments." Youngstown State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1619950217448915.
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Rohe, Lena [Verfasser], Reinhard [Akademischer Betreuer] Well, Nicole [Akademischer Betreuer] Wrage-Mönnig, Klaus [Akademischer Betreuer] Dittert, and Heinz [Akademischer Betreuer] Flessa. "Nitrous oxide from fungal denitrification - Pure culture and soil studies using stable isotope and microbial inhibitor approaches / Lena Rohe. Gutachter: Nicole Wrage-Mönnig ; Klaus Dittert ; Heinz Flessa. Betreuer: Reinhard Well." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2014. http://d-nb.info/1064148298/34.
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丁天佑. "Correlation of electrochemical behavior of montmorillonite on microbial inhibition charcteristics." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/89142312136329333808.
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Martinho, Mariana Agostinho Marques. "Microbial warfare: identification of microbial weapons in Streptococcus spp. colonizing the nasopharynx." Master's thesis, 2018. http://hdl.handle.net/10362/37049.
Full textAbstract:
The microbiota of the nasopharynx is a niche inhabited by several microorganisms including bacteria that are strict commensals and others that are pathobionts. Streptococcus pneumoniae is one of the latter. It is a major cause of morbidity and mortality worldwide being responsible for about 0.7 million deaths per year among children with less than 5 years of age.
With the rising numbers of antibiotic-resistant bacteria, infections are increasingly difficult to treat and there is a need for new antimicrobial therapies. Currently 20-30% of pneumococcal disease worldwide are caused by multidrug resistant strains.
Commensal streptococci of the respiratory tract could be used as a promising alternative to antibiotics as some produce antimicrobial molecules, called bacteriocins with narrow-spectrum activity against other bacteria.
The aim of this thesis was to identify commensal streptococci strains that would be able to inhibit S. pneumoniae strains, and to identify the bacteriocin loci in their genome potentially responsible for the observed phenotype.
Inhibitory assays to assess inhibitory profiles of streptococcal strains against a collection of pneumococci were done. Whole-genome sequencing (WGS) was done in selected streptococci strains and the data was analyzed for the presence of putative bacteriocin loci.
Three Streptococcus mitis strains had high inhibitory activity against S. pneumoniae strains while being immune to them. These strains had low inhibitory activity against other commensal streptococci strains. WGS analysis identified putative bacteriocin loci in these strains. Two blp and three lantibiotic putative loci were found in S. mitis strains.
The results obtained in this thesis show that there are commensal streptococci strains capable of inhibiting S. pneumoniae which could be of interest for further studies aiming to develop alternatives to antibiotics.
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Claro, Miguel Santos. "Flavobacterium as a microbial tool to protect plants from phytopathogenic fungi." Master's thesis, 2021. http://hdl.handle.net/10773/33458.
Full textAbstract:
As the world progresses towards a more sustainable agriculture, research for more ecological and sustainable alternatives for chemical fertilizers/pesticides are considered a valuable strategy. In this work, an attempt at elucidating antifungal capacity in Flavobacterium (49 strains) was made. The bacterial strains were grown in vitro with three different phytopathogenic fungi (Fusarium oxysporum, Macrophomina phaseolina and Botrytis cinerea). Biochemical responses after interaction in vitro were analysed from both organisms (bacterium and fungus). Flavobacterium strains evidenced antifungal properties against the three analysed fungi. However, F. oxysporum and B. cinerea were observed to be the most affected. Tests evidenced the influence of Flavobacterium strains mainly by contact inhibition in F. oxysporum , a mixed influence of volatile and contact inhibition in M.phaseolina and mainly volatile inhibition in B. cinerea. Flavobacterium strain J5 was observed to have antifungal properties against all phytopathogenic fungi used in this study. Overall biochemical responses of fungi to the presence of selected bacterial strains, evidenced oxidative damage and triggered antioxidant responses. However, some bacterial strains were demonstrated to be also negatively affected by the presence of fungi. Considering the results, the strains of the Flavobacterium genus used showed antifungal potential, but were also affected by the fungi, inducing the bacterial antioxidant response which, when not effective, led to oxidative damage.À medida que o mundo progride ao encontro de uma agricultura mais sustentável, a pesquisa de novas alternativas, mais ecológicas e sustentáveis, para a utilização de fertilizantes e pesticidas químicos são considerados uma estratégia valiosa. Neste trabalho, uma tentativa de elucidar a capacidade antifúngica de 49 estirpes bacterianas do género Flavobacterium foram feitas. As estirpes foram crescidas in vitro com três fungos fitopatogénicos (Fusarium oxysporum, Macrophomina phaseolina, Botrytis cinerea). Respostas bioquímicas foram analisadas após a interação in vitro de ambos os organismos (bactéria e fungo). As estirpes de Flavobacterium evidenciaram propriedades antifúngicas contra os três fungos analisados, no entanto, F. oxysporum e B. cinerea foram observados como sendo os mais afetados pelas estirpes. Testes evidenciaram a influência das estirpes de Flavobacterium, maioritariamente de inibição de contacto em F. oxysporum, uma influência mista de inibição volátil e de contacto em M. phaseolina e uma influência principalmente de inibição volátil em B. cinerea. A estirpe do género Flavobacterium, J5, foi observada como tendo propriedades antifúngicas para todas as espécies de fungos fitopatogénicos utilizados neste estudo. Em geral, as respostas bioquímicas dos fungos à presença das estirpes selecionadas, evidenciaram danos celulares e respostas antioxidantes. No entanto, algumas estirpes demonstraram ser negativamente afetadas pela presença dos fungos. Considerando os resultados, as estirpes utilizadas do género de Flavobacterium demonstraram potencial antifúngico, mas também foram afetadas pelos fungos, induzindo a resposta antioxidante que quando não foi eficaz conduziu ao dano oxidativo.
Mestrado em Biologia Aplicada
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Rodrigues, L. R. "Biosurfactants production by probiotic bacteria and inhibition of voice prostheses microbial colonization." Doctoral thesis, 2005. http://hdl.handle.net/1822/4632.
Full textAbstract:
Tese de doutoramento em Engenharia Química e Biológica.The main purposes of this thesis were the optimization of fermentation conditions for the production of biological antifouling agents, namely biosurfactants from probiotic bacteria, in order to develop new strategies for the prevention of microbial colonization of silicone rubber voice prostheses. Probiotic bacteria Lactococcus lactis 53 and Streptococcus thermophilus A were found to be biosurfactant¬producing strains. The improvement of the standard culture medium for biosurfactant production by response surface methodology, using a compilation of mathematical and statistical techniques, was used and an effective increase in the production yields was achieved. Economical alternatives were pursed using non conventional low cost raw materials as molasses or cheese whey instead of synthetic medium. An improvement of biosurfactants production yields with 60 to 80% medium preparation costs reduction was achieved. The ability of the biosurfactants obtained from probiotic bacteria to inhibit adhesion of microbial strains isolated from explanted voice prostheses to silicone rubber surfaces with and without an adsorbed biosurfactant layer was studied in a parallel plate flow chamber. Biosurfactants produced by the L. lactis 53 and S. thermophilus A reduced about 90% both deposition rates and number of adhering microorganisms after 4 hours. The biosurfactant obtained from S. thermophilus A proved to be much more efficient against Rothia dentocariosa GBJ 52/2B that is the most frequently isolated bacteria in the group of patients whose prostheses fail after a short time of use forcing replacement. An artificial throat model was used to assess the influence of biosurfactants from probiotic bacteria on the formation of voice prosthetic biofilms. Both biosurfactants were found to be antimicrobial agents and greatly reduced microbial numbers on prostheses and also induced a decrease in the airflow resistance of voice prostheses after biofilm formation. The key components of the crude biosurfactant mixtures produced by L. lactis 53 and S. thermophilus A, including their molecular composition (by Fourier transform infrared spectroscopy), elemental composition (by X-ray photoelectron spectroscopy), molecular mass (by mass spectrometry) and monosaccharide composition (by gas-liquid chromatography) were studied. Moreover, partial functional characterization was established using the following techniques: blood agar test, oil spreading test, critical micelle concentration determination, antimicrobial activity and anti-adhesion test. Finally, desorption of biosurfactants from silicone rubber and their stability at several pH were evaluated. The most surface-active fractions isolated from the crude biosurfactant mixtures were found to be rich in glycoproteins and glycolipids for L. lactis 53 and S. thermophilus A, respectively. In addition, these fractions showed antimicrobial and anti-adhesive activities against microbial strains isolated from explanted voice prostheses. Furthermore, the most surface-active fractions stay adsorbed onto silicone rubber surfaces up to 2 months at effective concentrations against microbial colonization. Therefore an increase in voice prostheses lifespan is achievable, as well as the consequent reduction of the health costs associated with prostheses replacement.
A presente tese teve como principais objectivos a optimização das condições fermentativas para a produção de compostos inibidores da adesão microbiana, nomeadamente biosurfactantes, por bactérias probiólicas; de forma a desenvolver novas estratégias de prevenção da colonização microbiana das próleses da fala. Demonstrou-se que as bactérias probióticas Lactococcus lactis 53 e Streptococcus thermophilus A são estirpes produtoras de biosurfactantes. O melhoramento dos meios de cultura para a produção de biosurfactantes foi efectuado usando a metodologia de optimização factorial, fazendo recurso a uma série de ferramentas matemáticas e estatísticas, tendo-se obtido um efectivo aumento dos rendimentos de produção. Alternativas mais económicas foram desenvolvidas usando matérias-primas não convencionais de baixo custo, como os melaços e o soro de queijo. Atingiu-se uma melhoria razoável dos rendimentos de produção de biosurfactantes tendo sido estimado um decréscimo de 60-80% dos custos associados. A capacidade dos biosurfactantes de inibir a adesão de microorganismos isolados de próteses da fala (removidas de doentes) a superfícies de borracha de silicone com e sem uma camada de biosurfactante adsorvida, foi estudada usando para o efeito uma célula de fluxo laminar. Ambos os biosurfactantes promoveram uma redução de cerca de 90% das taxas de deposição iniciais de microorganismos, bem como do número tolal de microorganismos aderidos ao final de 4 horas. O biosurfactante obtido a partir de S. thermophilus A provou ser muito mais eficiente na inibição da adesão de Rothia dentocariosa GBJ 52/2B que é a bactéria mais frequentemente isolada em doentes cujas próteses falham após um curto período de uso, forçando a sua substituição. Um modelo de garganta artificial com próteses da fala foi utilizado para estudar o efeito dos biosurfactantes na formação de biofilmes. Ambos os biosurfactantes apresentaram actividade antimicrobiana e reduziram significativamente o número de microorganismos presentes nas próteses, bem como promoveram um decréscimo da resistência à passagem de ar através da válvula da prótese. Os biosurfactantes produzidos por L. lactis 53 e S. thermophilus A foram parcialmente purificados numa coluna de interacção hidrofóbica. As estruturas físico-químicas e características funcionais das fracções isoladas foram estudadas. A composição molecular (por FTIR) , a composição elementar (por XPS), a massa molecular (por espectrometria de massa) e a composição em açúcares simples (por cromatografia gasosa) foram estudadas. A caracterização funcional foi estabelecida com recurso a técnicas como: teste do agar de sangue para avaliar a actividade hemolítica; teste para avaliar a dispersão de óleos; determinação da concentração micelar crítica e a determinação das actividades antimicrobianas e anti-adesivas. Adicionalmente foi efectuado um estudo da desorção das fracções activas ligadas a superfícies de borracha de silicone, bem como da sua estabilidade a vários valores de pH. Concluiu-se que as fracções com maior actividade de superfície obtidas a partir de L. lactis 53 e S. thermophilus A são ricas em glicoproteinas e glicolipidos, respectivamente. Estas fracções demonstraram possuir actividade antimicrobiana, bem como anti-adesiva contra os microorganismos isolados de próteses de doentes. Finalmente, verificou-se que as fracções com maior actividade de superfície permanecem adsorvidas à borracha de silicone até cerca de 2 meses em concentrações inibitórias da colonização microbiana, o que poderá permitir um aumento do tempo de vida das próteses da fala e consequentemente reduzir os custos de saúde associados à sua frequente substituição
Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/4700/2001.
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Wang, Shuyi. "Microbial Impacts of Selected Pharmaceutically Active Compounds Found in Domestic Wastewater Treatment Plants." Diss., 2009. http://hdl.handle.net/10161/1235.
Full textAbstract:
Large amounts of human pharmaceutical products are consumed worldwide. Many drugs and their metabolites, referred to as pharmaceutically active compounds (PhACs), are not fully metabolized prior to household discharge resulting in their common occurrence in wastewater treatment plants (WWTPs). In most instances, WWTPs present the first treatment opportunity for removing PhACs and preventing significant environmental exposure. Because most municipal WWTPs rely on the microbial component of the activated sludge process, there is a need to estimate the influence of PhACs in wastewater influent on the activated sludge microbial communities and the treatment performance of WWTPs. The objective of this dissertation was to determine the impact of selected PhACs (i.e., ketoprofen, naproxen, clofibric acid, carbamazepine and gemfibrozil) on activated sludge microorganisms and key individual microbial species in domestic wastewater treatment. Analyses were performed in batch reactors initially and then in laboratory-scale sequencing batch reactors (SBR) which mimic WWTP operations. Ammonia oxidizing bacteria (AOB) were selected as indicator organisms because of their importance in wastewater treatment and demonstrated sensitiveness to toxic compounds.
The batch experiments results suggested that microbial growth inhibition was correlated to organic loadings. In the presence of 0.2% (v/v) ethanol, significant inhibition, ranging from 34 to 43%, was observed for all PhACs other than clofibric acid.
Nitrification inhibition studies using Nitrosomonas europaea, a model AOB strain showed that ketoprofen, naproxen, carbamazepine and gemfibrozil inhibited nitrite production. The corresponding maximum nitrification inhibition rates were 25, 29, 22 and 26%, respectively. Inhibition was shown to increase with PhAC concentration for concentrations greater than 0.1 µM. Results from membrane integrity tests suggest that the inhibition may be due to the disturbance of the cell membrane by PhACs and such inhibition was shown to be irreversible.
Even though PhACs were shown to inhibit the nitrification rate in pure culture studies, the performance of SBRs exposed to individual PhACs was not adversely affected neither in terms of COD nor ammonia removal. Microbial fingerprinting for both total bacteria and AOB confirmed that no significant shifts occurred when microbial communities were exposed to PhACs. However, some PhACs introduced in binary mixture were found to both inhibit the nitrification of N. europaea as well as the performance of SBRs. The mixture composed of 0.5 μM ketoprofen and 0.5 μM naproxen showed significant inhibition (25%) on the nitrite production of N. europaea although neither 0.5 μM ketoprofen nor 0.5 μM naproxen had significant effect when presented alone. Similarly, both COD and ammonia removal were significantly impacted by binary mixtures of PhACs. These results suggest that mixture effects can play an important role in an overall treatment's nitrification potential and this phenomenon should be further investigated.
Dissertation
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Jiao, Lei. "Mechanisms underlying the microbial exposure-mediated inhibition of allergic reactions : crucial roles of dendritic cells and natural killer cells." 2009. http://hdl.handle.net/1993/21487.
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Rohe, Lena. "Nitrous oxide from fungal denitrification - Pure culture and soil studies using stable isotope and microbial inhibitor approaches." Doctoral thesis, 2014. http://hdl.handle.net/11858/00-1735-0000-0023-9969-1.
Full textAbstract:
Das Spurengas Lachgas (N2O) trägt zur Klimaerwärmung und Zerstörung der Ozonschicht in der Atmosphäre bei. Mit einem Anteil von ca. 70% sind landwirtschaftliche Böden weltweit Hauptverursacher der hohen anthropogenenN2O Emissionen. N2O entsteht in Böden durch verschiedene mikrobiologische Prozesse, bei denen N2O unter anderem aus düngerbürtigem N gebildet wird. Die Entwicklung effektiver Minderungsmaßnahmen wird erst möglich, wenn ein Verständnis der N2O Quellprozesse und ihrer Dynamik in Böden vorhanden ist.
In dieser Studie wurde die Denitrifikation als ein Quellprozess untersucht, der zusammen mit Nitrifikation und Nitrifizierer-Denitrifikation hauptsächlich für die N2O Emissionen aus Böden verantwortlich ist. Die Denitrifikation beschreibt die Reduktion von Nitrat (NO3-) zu N2, wobei Nitrit (NO2-), Stickstoffmonoxid (NO) und N2O Zwischenprodukte dieses Reaktionsweges sind. Lange Zeit galten heterotrophe Bakterien als alleinige Verursacher von N2O Emissionen aus der Denitrifikation. Im Jahr 1972 wurde allerdings in Versuchen mit Pilzreinkulturen nachgewiesen, dass auch Pilze in der Lage sind, N2O über die Denitrifikation zu bilden. Zwei Jahrzehnte später wurde gezeigt, dass den meisten Pilzen das Enzym N2O-Reduktase fehlt. Somit ist nicht N2, sondern N2O das hauptsächliche Endprodukt der pilzlichen Denitrifikation. Dies lässt vermuten, dass die Bildung von N2O durch pilzliche Denitrifikation noch unterschätzt wird, vorausgesetzt Pilze und Bakterien haben ähnliche Prozessraten. Bisher wurde jedoch nicht ausgiebig erforscht, welchen Anteil die einzelnen mikrobiellen Gemeinschaften an der N2O Bildung tatsächlich haben.
Zur Unterscheidung der N2O Bildungsprozesse in Bezug auf die beteiligten Mikroorganismen stellt die Isotopenanalyse von N2O eine vielversprechende Anwendung dar. Vor allem die 15N-Positionspräferenz im N2O (SP = site preference, d.h. die Differenz zwischen den δ15N-Werten der außenständigen und zentralen N-Atome im linearen N2O-Molekül) aus der Denitrifikation zeigte starke Unterschiede zwischen Reinkulturen einiger Bakterien (SP = -11 bis 0 ‰) und zwei untersuchten Pilzen (SP ~ 37 ‰). Jedoch wurden Bakterienreinkulturen bisher ausgiebiger untersucht als Pilzreinkulturen, auch wenn bekannt ist, dass sich die beteiligten Enzyme bei der Denitrifikation, bis auf die NO-Reduktase, zwischen Bakterien und Pilzen nicht unterscheiden. Die verschiedenen NO-Reduktasen sind vermutlich die Ursache für die unterschiedlichen SP-Werte des von Pilzen und Bakterien produzierten N2O. Des Weiteren wurde bei Bakterien ein Austausch der Sauerstoffatome von Zwischenprodukten der Denitrifikation und dem umgebenden Wasser gefunden, der zwischen 4 und 100% beträgt. Ob es einen solchen Sauerstoffaustausch auch bei Pilzen gibt, ist bisher jedoch unerforscht. Würde der Sauerstoffaustausch bei pilzlicher Denitrifikation nicht erfolgen, ermöglichte dies neben der unterschiedlichen SP eine weitere Unterscheidung der Herkunft des N2O. Der Sauerstoffaustausch würde signifikante Unterschiede in der O Isotopensignatur im N2O pilzlicher bzw. bakterieller Herkunft verursachen.
In der vorliegenden Studie, die Aufschluss über die pilzliche N2O Produktion aus der Denitrifikation geben soll, wurden drei Hauptthemen behandelt. In einem Isotopen-Tracerexperiment mit
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CHING, CHIH-HAO, and 荊智豪. "Preparation of Fermented Rice Kojic Broth and Its Application in the Inhibition of Enzymatic Browing and Microbial Growth on Apple Dices and Apple Juice." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/qc534g.
Full textAbstract:
碩士弘光科技大學
食品科技所
103
Fresh-cut fruits and vegetables are convenient and nutritional for people.Therefore, fresh-cut fruits and vegetables have become more popular in recent years. However, before selling, these products will be treated in some minimal processing steps, such as washing, peeling and cutting, which make the fruit tissue injured and then increased the risk of microbial contamination. The contamination of microbial not only reduces the shelf-life of products but also causes foodborne outbreaks. So techniques of lowering the microorganism count and inhibit enzyme system are commonly used. The objectives of this research are providing safety and fresh products, and extending product’s shelf-life. Organic acid including kojic acid can be produced from fermented rice broth but also can inhibit microbial and enzyme browning efficacy.This study was carried out to determine effects of yeast strains and fermented on organic acid including kojic acid for the production of Taiwan glutinous rice.Fermentation of steamed and non-steamed rice were inoculated with different commercial strains of yeast (Scharomyces cerevisiae). At the 15th days of cultured yeast, rice kojic broth were centrifugal and separated then used clarified liquor for chemical analyses.The highest fermented rice kojic broth include organic acid and Kojic acid was designated to studied . Treatment of reverse osmosis water、10ppm kojic acid solution、20% fermented rice kojic broth、10ppm chlorine dioxide solution that fresh-cut apple to remove the peel then soak, pureed with different solution respectively，stored at 5 ± 1。C for 0、1、2、3 days ；juice for 0、8、16、24 hours to analyze.Results indicate that fermented rice kojic broth reduced dices apple and juice of total plate count in the range of 4.1 and 2.8（log cfu/ml） values to approach chlorine dioxide significantly (P < 0.001).L values of HunterLab's color measurement instruments by 20% fermented rice kojic broth brightness high then others (apple dices over 4.0)，the juice color parameters of the initial stage would not have been significant deviation ( over 0.4 ) but external color when viewed by the naked eye. Optical density results indicate fermented rice kojic broth inhibition on apple juice browning for 0、8、16、24 hours during the early to end storage，besides the consumer sensory evaluation analysis to the obtain overall data of 20% fermented rice kojic broth treatments on apple dices and juice preferences also significant batter than others. The dual effectiveness of fermented rice kojic broth to inhibit enzymatic browning and total bacterial slowing the growth may allow this compound to achieve a prominent role in improving the quality and safety of products in the fresh-cut apples and other food industries;furthermore avoid the use of potable water instead of water containing chemical disinfection on fruits and vegetables products processing.
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Wei, Huei-Chi, and 韋慧琦. "Evaluation of the quality and microbial inhibition of sliced ham spray coated with Chinese mahogany (Toona sinensis) extracts and stored at 15±2℃ for 21 days." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/43870753698188953132.
Full textAbstract:
碩士國立中興大學
動物科學系所
103
Consumption of ready-to-eat (RTE) foods has considerably increased due to their convenience. But RTE meat products were easily polluted with microorganism during preparation and resulted in outbreak of foodborne illness. Synthetic preservatives play an important role in RTE meat products, but they always know as negative response for human health. At present, a lot of scientific studies are looking for nature antimicrobial compounds from plants to replace synthetic preservatives in food system. Toona sinesis was rich in polyphenolic compounds that has excellent antimicrobial and antioxidant activities. Therefore, the aims of this study were (1) to determine the total phenol and total flavonoids concentrations in T. sinensis by ultrasound-assisted extraction and the minimum inhibitory concentration of Listeria monocytogenes; (2) to screen the different levels of T. sinensis extracts (0, 125, 250 and 500 μg/mL) spray coating on sliced ham to control the growth of L .monocytogenes and S. aureus stored at 15±2℃ for 5 days and (3) to evaluate the quality and microbial inhibition of sliced ham spray coated with different levels of T. siensis extracts then packed with vacuum package and stored at 15±2℃ for 21 days. The results showed that the extracts of T. sinensis treated by ultrasonication for 80 min had the highest total phenol and total flavonoids content. The minimum inhibitory concentration of T. sinesis extract for L. monocytogenes was 1.95 μg/mL. The inhibition of pathogen bacteria (L. monocytogenes and S. aureus ) test showed that the L. monocytogenes and S. aureus counts increased with storage time. At day 5, sliced ham treated with all of T. sinensis extracts and PC were significantly lower than control. The chemical compositions of all treatments were slightly different. The pH value of all lots were stable and ranged as 6.21 to 6.38 during storage time. During storage, L* and a* value of all lots were slightly varied and b* value was increased with storage days. The total plate count of control, PC and 0 μg/mL of T. sinesis extract were significantly higher than treated with T. sinensis extracts at the end of storage. However, sliced ham treated with 500 μg/mL T. sinensis extracts still maintained the lowest count. During 21 days of storage, the anaerobic of sliced hams treated with 500 μg/mL of T. sinensis extracts hold lower count. Sliced ham spray-coating 250 and 500 μg/mL of T. sinensis showed lower than 102 CFU/g of lactic acid bacteria count during storage. Otherwise, the control, PC and 125 μg/mL maintained lower than 102 CFU/g of lactic acid bacteria count at the early storage time (0-14) then increased up to 104 CFU/g at the end of storage. The VBN of all lots maintained stable with storage time and spray-coating above 250 μg/mL of T. sinensis showed lower than control. Analysis of sensory panel, all sensory items of sliced ham of all lots were decreased as storage time. However, except the 250 μg/mL of T. sinensis had lower value, other T. sinensis treatments had no significantly different, and all score values were higher than 4. Sliced ham treated by over 250 μg/mL of T. sinensis extracts not only retard the growth of microorganism but also maintain a good sensory profiles in this study.
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HO, TSUNG-I., and 何宗奕. "Cloning of microbial inhibiting genes from Agaricus bisporus." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/25337999752321953824.
Full textAbstract:
碩士國立新竹教育大學
應用科學系碩士班
102
Abstract This research study focuses primarily on finding new forms of anti-bacterial genes in mushrooms (Agaricus bisporus). By using membrane impermeability test we were able to screen out two clones, AB-Y1a and AB-Y1b, that were capable of causing bacteria membrane impermeability. The misuse and overuse of antibiotics have brought up a serious issue of bacteria becoming more and more potent on resisting traditional antibiotics. For many years, fungus has been used in medical studies to develop new medicines and I have therefore chosen fungus to be the target of my study. mRNA pool of Agaricus bisporus was reverse-transcribed and inserted onto pET-23a expression vector to form a cDNA library. All cDNA clones, without a pre-determined selection of genes, were subjected to Trypan blue exclusion assay to examine how the cloned genes had affected bacterial membrane impermeability and to determine whether bacteria was killed. Anti-bacterial growth curve experiment showed that, after induction of AB-Y1a, OD600 value of the bacteria medium decreased to 1/5 of that of non-induced control medium, and that, after induction of AB-Y1b, OD600 value of the bacteria medium decreased to 1/2 of that of non-induced control medium, indicating both AB-Y1a and AB-Y1b are capable of suppressing bacterial growth. Sequence analysis on AB-Y1a showed that AB-Y1a is a glycosylphosphatidylinisotol anchored protein, GPI-AP. AB-Y1a is likely a secretion protein and its first 20 amino acids contains a signal peptide that can be cleaved before the protein is secreted. Through GPI, AB-Y1a is likely able to bind to the outside of cell membranes and cause abnormities and interferences that, in turn, suppress bacterial growth. Sequence analysis showed that AB-Y1b is a helicase. AB-Y1b is speculated to interfere with bacterial transcription and, therefore, impedes bacterial replication. Moreover, AB-Y1b contains a P-loop structure that interacts with ATP/GTP. It is therefore probable that this P-loop competes with bacteria for ATP and in turn hinders bacterial growth.
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Al-Nasiri, Ghofran. "Microencapsulation of Natural Antimicrobial Agents to Minimize Loss from Food Packaging Films." Thesis, 2019. https://vuir.vu.edu.au/40070/.
Full textAbstract:
The inherent volatility and/or heat sensitivity of many natural antimicrobial (AM) additives can be detrimental to their widespread use in commodity polymer packaging film formulations. In this study, beta-cyclodextrin (β-CD) inclusion complexes with naturally-derived AM agents: thymol, carvacrol, and linalool were prepared using a co-precipitation technique. The complexes were optimised and then characterised by techniques including thermal analysis. They were then incorporated into low-density polyethylene (LDPE) films with AM agents added directly for comparison. The subsequent release of the AM agents into food simulants was studied followed by an investigation of the efficacy of the films in vitro against selected bacteria. The films were later tested on real foods to assess their potential for controlling microbial growth and lipid oxidation.
In the initial experiments, conditions for synthesising the β-CD/AM agent complex including solvent composition, temperature, reaction time, and total solvent volume were investigated to optimise the inclusion efficiency (IE) and yield. Electrospray ionization mass spectrometry and gas chromatography were used to confirm the formation and quantify the amount AM agents that were encapsulated, absorbed onto the surface, or remaining in the filtered solvent. The systematic optimisation of the conditions improved both the yield of the complex and the IE of the AM agents. Using a 1:1 mole ratio of the AM agent to β-CD, the optimised parameters resulted in maximum yields of 87, 84 and 86% (w/w) for thymol, carvacrol and linalool respectively with IE’s close to 100% (w/w) for each agent.
The kinetics of the thermal decomposition of the optimised β-CD and complexes of the three AM agents were then investigated using thermogravimetric analysis. Under a linear temperature ramp and in the degree of conversion, α, domain: 0.1 ≤ α ≤ 0.8, the major decomposition steps of the β-CD, and complexes with carvacrol, linalool and thymol occurred at ca. 300°C and followed Avrami-Erofeev kinetics with apparent activation energies, Ea, of: 156 ± 6, 107 ± 7, 96 ± 3 and 110 ± 3 kJ mol-1 respectively. Below ca. 300°C there were staged mass losses from each of the complexes that were not observed for the neat β-CD. These were attributed to lower energy binding interactions and accounted for a little over half of the available guest species in the complex in each case. Lower temperature mass losses for β-CD complexes with carvacrol (ca. 140 to 230°C) and linalool (ca. 95 to 150°C) were analysed and found to be adequately fitted by second-order kinetics with apparent Ea values of: 37 ± 1 and 69 ± 6 kJ mol-1 respectively. The results suggest the optimized complexes are generally thermally stable and would potentially be suitable for high-temperature extrusion processes with acceptably low losses.
The next experiments involved the incorporation of the AM agents into LDPE films either directly or encapsulated in β-CD. Quantification of the AM agents was performed immediately following thermal processing, then six and thirty days after the film samples were stored in an open atmosphere. After six days, no AM agent was detected in the films where the agent was added directly to the film whereas the films containing encapsulated agents showed only small decreases in the concentrations of the agents up to 30 days. The migration of AM agents from LDPE films into 95% (v/v) ethanol/water mixtures food simulants at 4℃ was adequately described using first-order kinetics and Fick’s second law of diffusion. For the AM agents added directly to the film, the initial release rates were between four and eight times greater than those of the encapsulated agents. Similarly, the diffusion coefficients of the free agents were ca. four to five times greater than the encapsulated agents.
The free and encapsulated natural AM agents incorporated into LDPE film were tested against Escherichia coli (ATCC 25922) in order to assess the potential of the AM inclusion complexes for use in food packaging films. The direct incorporation of the complexes in the film formulations resulted in little inhibition of the target bacterium as assessed by the agar diffusion method even with AM levels as high as 5% (w/w). In comparison, levels of 2% (w/w) of free thymol and carvacrol added directly to the film demonstrated inhibition. The addition of glycerol to the film formulations was investigated as a means of facilitating the AM agent from the complex. A concentration of 1% (w/w) of glycerol in the film formulation was found to result in microbial inhibition which increased with additional glycerol. The use of 2% (w/w) glycerol resulted in a more pronounced inhibition of targeted microorganism. Upon the addition of glycerol, all of the films showed AM activity against the target bacterium with the exception of those containing linalool in either the free or encapsulated forms. Upon the addition of 2% (w/w) of glycerol to the film formulation, encapsulated thymol at a concentration of 2% (w/w) was more effective than encapsulated carvacrol at a concentration of 3% (w/w) against E. coli with zones of inhibition of 30.70 ± 0.72 and 29.61 ± 0.86 mm respectively.
In the final experiments, the LDPE films containing encapsulated thymol were tested on real food systems. The level of thymol was 1 to 3% (w/w) relative to the LDPE and glycerol was added in order to obtain the optimum controlled release. In the case of packaged minced beef inoculated with E. coli, no inhibition was observed when the concentration of encapsulated thymol was 3% (w/w) with 2% (w/w) glycerol, however, the same film reduced E. coli growth by 0.7 log10 CFU g-1 on chicken breast fillets compared with the control during storage at 4℃ for 12 days. The growth of E. coli was found to be affected by the temperature at 4℃ whereby the bacterial counts remained relatively low with slow growth over the test period under refrigeration. However, when the temperature increased to 10℃ it was also found that the presence of coliforms interfered with growth of E. coli and, in general, the films containing encapsulated thymol effectively reduced coliform growth. Analysis of the antioxidant (AO) activity of films using the diphenyl-picrylhydrazyl (DPPH) radical assay showed a 71% reduction in DPPH concentration for the LDPE/thymol/β-CD films containing 3% (w/w) thymol. Furthermore, a film comprised of 1% (w/w) thymol with glycerol stored at room temperature for 20 months showed a reduction by 23% in DPPH concentration confirming that the films are suitable for extended storage. Analysis of the formation of thiobarbituric acid reactive substances on packaged minced beef showed decreases in lipid oxidation of 60 and 75% for films containing 1% and 3% (w/w) thymol in the film respectively. The films therefore show promise for the dual purpose of AO and AM activity in order to prolong the shelf-life of selected food products.
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Lin, Chi-An, and 林祈安. "Effect of novel MAP on inhibiting microbial growth in Chinese ready-to-eat food products at ambient temperature." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/80552050692442036355.
Full textAbstract:
碩士輔仁大學
食品營養學系
89
Ready-to-eat products stored at ambient temperature (25oC or up) were studied in this study, and the inhibitory effect on microbial growth and the retention of quality by modified atmosphere packaging (MAP) were investigated. MAP model system was constructed to assess the inhibitory effect on microbial growth at ambient temperature, and the effectiveness associated with ethanol or limonene was also achieved. Subsequently, the modified atmosphere environment was applied to ready-to-eat food. More than 200 colonies were observed from the control stored at 37℃, 48hr in the model study; however, less microbial growth was noticed under 30-40% CO2 environment. MAP (CO2:O2:N2=30:5:65) incorporated with ethanol vapor functioned inhibiting E. coli growth, and the effectiveness related to the amount of ethanol vapor. Sushi packed under modified atmosphere containing 0.05% ethanol vapor was found no increase in cell number after 2 days, either at 18 or 25oC. Use of limonene associated with MA also performed inhibiting microbial growth; however the efficiency was not as good as ethanol vapor. In the study of noodle salad, cells were found increasing sharply in all packaged products at 25oC after 24hr. Apparently, MA incorporated with ethanol vapor is effective on inhibiting microbial growth in certain ready-to-eat food stored at ambient temperature, thus the extension of shelf life is achieved.
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Iverson, Chad. "Identification of glutathione S-transferase inhibiting natural products from Matricaria chamomilla and biotransformation studies on oxymatrine and harmine." 2010. http://hdl.handle.net/1993/4150.
Full textAbstract:
This thesis describes the results obtained from the phytochemical analysis of Matricaria chamomilla, and the microbial transformation of oxymatrine (85) and harmine (87), as summarized below.
1. Chemical investigation of the crude methanolic extract of Matricaria chamomilla resulted in the isolation of a new natural product, matriisobenzofuran (72), along with four known compounds: apigenin (73), apigenin-7-O-β-glucopyranoside (74), scopoletin (75), and fraxidin (76). The structures of compounds 72-76 were elucidated with the aid of extensive NMR and mass spectroscopic studies. All of the aforementioned compounds showed moderate to good inhibitory activities against glutathione S-transferase, an enzyme which has been implicated in the resistance of cancer cells to chemotherapeutic agents. These compounds were also evaluated for antioxidant activity and displayed moderate to good free radical scavenging activity. Additionally, compounds 72-76 were screened for anti-leishmanial activity. Compounds 75 and 76 were significantly active in this assay, while the remaining compounds were weakly active. In the antibacterial and antifungal assays, compounds 72-76 were not active.
2. The second part of this thesis deals with the biotransformation studies on oxymatrine (85) and harmine (87). Oxymatrine (85) was metabolized to the deoxy analogue, matrine (84) by Penicillum chrysogeneum (ATCC 9480), Cunninghamella bainieri (ATCC 9244), Cunninghamella blakesleena (ATCC 9245 and 8688A), Curvularia lunata (ATCC 12017), and Fusarium sp. In the time-based analysis of this transformation, the metabolism of oxymatrine (85) could be detected after 48 hours of incubation. Additionally, incubation of harmine (87) with Mucor plumbeus (ATCC 4740) resulted in the isolation of harmine-N-oxide (94). The biotransformed products (84 and 94) were identified using IR, UV, NMR, and mass spectroscopic techniques. Compound 94 was evaluated for its ability to inhibit the enzyme acetylcholinestrase, whose overexpression has been linked to Alzheimer’s disease, and was found to possess weaker activity than harmine (87).