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1
Conrad, R., B. Schink, and T. J. Phelps. "Thermodynamics of H2-consuming and H2-producing metabolic reactions in diverse methanogenic environments under in situ conditions." FEMS Microbiology Letters 38, no. 6 (1986): 353–60. http://dx.doi.org/10.1111/j.1574-6968.1986.tb01748.x.
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Strąpoć, Dariusz, Flynn W. Picardal, Courtney Turich, et al. "Methane-Producing Microbial Community in a Coal Bed of the Illinois Basin." Applied and Environmental Microbiology 74, no. 8 (2008): 2424–32. http://dx.doi.org/10.1128/aem.02341-07.
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ABSTRACT A series of molecular and geochemical studies were performed to study microbial, coal bed methane formation in the eastern Illinois Basin. Results suggest that organic matter is biodegraded to simple molecules, such as H2 and CO2, which fuel methanogenesis and the generation of large coal bed methane reserves. Small-subunit rRNA analysis of both the in situ microbial community and highly purified, methanogenic enrichments indicated that Methanocorpusculum is the dominant genus. Additionally, we characterized this methanogenic microorganism using scanning electron microscopy and distribution of intact polar cell membrane lipids. Phylogenetic studies of coal water samples helped us develop a model of methanogenic biodegradation of macromolecular coal and coal-derived oil by a complex microbial community. Based on enrichments, phylogenetic analyses, and calculated free energies at in situ subsurface conditions for relevant metabolisms (H2-utilizing methanogenesis, acetoclastic methanogenesis, and homoacetogenesis), H2-utilizing methanogenesis appears to be the dominant terminal process of biodegradation of coal organic matter at this location.
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Sakai, Sanae, Hiroyuki Imachi, Yuji Sekiguchi, Akiyoshi Ohashi, Hideki Harada, and Yoichi Kamagata. "Isolation of Key Methanogens for Global Methane Emission from Rice Paddy Fields: a Novel Isolate Affiliated with the Clone Cluster Rice Cluster I." Applied and Environmental Microbiology 73, no. 13 (2007): 4326–31. http://dx.doi.org/10.1128/aem.03008-06.
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ABSTRACT Despite the fact that rice paddy fields (RPFs) are contributing 10 to 25% of global methane emissions, the organisms responsible for methane production in RPFs have remained uncultivated and thus uncharacterized. Here we report the isolation of a methanogen (strain SANAE) belonging to an abundant and ubiquitous group of methanogens called rice cluster I (RC-I) previously identified as an ecologically important microbial component via culture-independent analyses. To enrich the RC-I methanogens from rice paddy samples, we attempted to mimic the in situ conditions of RC-I on the basis of the idea that methanogens in such ecosystems should thrive by receiving low concentrations of substrate (H2) continuously provided by heterotrophic H2-producing bacteria. For this purpose, we developed a coculture method using an indirect substrate (propionate) in defined medium and a propionate-oxidizing, H2-producing syntroph, Syntrophobacter fumaroxidans, as the H2 supplier. By doing so, we significantly enriched the RC-I methanogens and eventually obtained a methanogen within the RC-I group in pure culture. This is the first report on the isolation of a methanogen within RC-I.
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Posewitz, M. C., P. W. King, S. L. Smolinski, et al. "Identification of genes required for hydrogenase activity in Chlamydomonas reinhardtii." Biochemical Society Transactions 33, no. 1 (2005): 102–4. http://dx.doi.org/10.1042/bst0330102.
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The eukaryotic green alga, Chlamydomonas reinhardtii, produces H2 under anaerobic conditions, in a reaction catalysed by an [FeFe]-hydrogenase. To identify genes that influence H2 production in C. reinhardtii, a library of 6000 colonies on agar plates was screened with sensitive chemochromic H2-sensor films for clones defective in H2 production. Two mutants of particular interest were fully characterized. One mutant, hydEF-1, is unable to assemble an active [FeFe]-hydrogenase. This is the first reported C. reinhardtii mutant that is not capable of producing any H2. The second mutant, sta7-10, is not able to accumulate insoluble starch and has significantly lowered H2-photoproduction rates in comparison with the wild-type. In hydEF-1, anaerobiosis induces transcription of the two reported C. reinhardtii hydrogenase genes, HydA1 and HydA2, indicating a normal transcriptional response to anaerobiosis. In contrast, the transcription of both hydrogenase genes in sta7-10 is significantly attenuated.
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Pham, Hanh Thi Kim, Anh Thi Ngoc To, and Anh Duong Tam Nguyen. "Collection of some microbial consortia producing hydrogen from anaerobic wastes." Science and Technology Development Journal 16, no. 1 (2013): 51–59. http://dx.doi.org/10.32508/stdj.v16i1.1396.
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The preparation of hydrogen-producing microbial consortia from three anaerobic digested sludges were carried out by four different pretreatment methods (heat – shock, acid, base and aeration treatment) as well as untreatment. The obtained microbial seeds have been estimated for their stability in fermentative hydrogen production by three consecutive batch fermentations under the same conditions of pH 6.5, room temperature and cultivation time and also investigated the H2 fermentation from different concentrations of glucose and xylose. Three microbial seeds have the most effective H2 production at 5 g/l of glucose or xylose after 48 h cultivation time. The sewage sludge pretreated at 80oC for 30 minutes shows the hydrogen yield of 1.27 mol/mol glucose and 0.82 mol/mol xylose. The sludge in the biogas tank pretreated at 60oC for 30 minutes has the hydrogen yield of 1.27 mol/mol glucose and 0.71 mol/mol xylose. The sludge of the Hoa Binh waste treatment plant pretreated at 60oC for 30 minutes presents the hydrogen yield of 1.31 mol/mol glucose and 0.66 mol/mol xylose.
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Subramanian, Venkataramanan, Alexandra Dubini, David P. Astling, et al. "ProfilingChlamydomonasMetabolism under Dark, Anoxic H2-Producing Conditions Using a Combined Proteomic, Transcriptomic, and Metabolomic Approach." Journal of Proteome Research 13, no. 12 (2014): 5431–51. http://dx.doi.org/10.1021/pr500342j.
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Bakonyi, Péter, Nándor Nemestóthy, and Katalin Bélafi-Bakó. "Comparative Study of VariousE. coliStrains for Biohydrogen Production Applying Response Surface Methodology." Scientific World Journal 2012 (2012): 1–7. http://dx.doi.org/10.1100/2012/819793.
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The proper strategy to establish efficient hydrogen-producing biosystems is the biochemical, physiological characterization of hydrogen-producing microbes followed by metabolic engineering in order to give extraordinary properties to the strains and, finally, bioprocess optimization to realize enhanced hydrogen fermentation capability. In present paper, it was aimed to show the utility both of strain engineering and process optimization through a comparative study of wild-type and genetically modifiedE. colistrains, where the effect of two major operational factors (substrate concentration and pH) on bioH2production was investigated by experimental design and response surface methodology (RSM) was used to determine the suitable conditions in order to obtain maximum yields. The results revealed that by employing the genetically engineeredE. coli(DJT 135) strain under optimized conditions (pH: 6.5; Formate conc.: 1.25 g/L), 0.63 mol H2/mol formate could be attained, which was 1.5 times higher compared to the wild-typeE. coli(XL1-BLUE) that produced 0.42 mol H2/mol formate (pH: 6.4; Formate conc.: 1.3 g/L).
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Wang, Yuan Yuan, Jian Bo Wang, Cheng Xiao Hu, and Yan Lin Zhang. "Effect of Various Pretreatment Methods of Inoculum on Biohydrogen Production." Advanced Materials Research 152-153 (October 2010): 902–8. http://dx.doi.org/10.4028/www.scientific.net/amr.152-153.902.
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Influence of different pretreatment methods applied on anaerobic mixed inoculum was evaluated for selectively enriching the hydrogen (H2) producing mixed culture using glucose as substrate. The cumulative H2 yield and H2 production rate were found to be dependent on the type of pretreatment procedure adopted on the parent inoculum. They could be increased by appropriate pretreatment methods, including use of heat, alkaline or acidic conditions. Along with the processing temperature and time of heat pretreatment and alkaline of alkali pretreatment increasing, the H2 yield increased and then declined, but it declined and then increased as the acidity of acid pretreatment increasing. Among the studied pretreatment methods, the heat pretreatment methods procedure enabled higher H2 yield and the maximum H2 production rate, then were alkali and acid pretreatment methods. When the inoculum was heat-treated at 80°C for 30 min, the highest cumulative H2 yield was obtained at 2152.0 mL, which was 53.20% higher than the control, and the maximum H2 production rate was 178.0 mL h-1, which was 122.0% higher than that of the Ctrl (138.0mL h-1).
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Hartmann, L., D. Taras, B. Kamlage, and M. Blaut. "A new technique to determine hydrogen excreted by gnotobiotic rats." Laboratory Animals 34, no. 2 (2000): 162–70. http://dx.doi.org/10.1258/002367700780457617.
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A new system, that allowed the monitoring of hydrogen (H2) excretion by gnotobiotic rats without affecting their defined microbial status, was developed. The system consists of an isolator containing a chamber for an experimental animal, and a life-support system (LSS). with a sampling port outside the isolator connected to it. H2 accumulation in the system was measured by analysing a defined volume of gas after removal. H2 concentrations were determined with an electrochemical cell or by gas chromatography. To validate this technique, H2 excretion by germ-free (GF) and mono-associated rats fed a chemically defined diet was measured after oral application of lactulose. Mono-associated rats had been obtained by colonizing GF rats with a H2-producing Clostridium perfringens type A strain isolated from human faeces of a healthy volunteer. Application of 50 mg lactulose to the mono-associated rats resulted in a significant increase in H2 excretion. The net H2 excretion was 7.82±1.28 ml H2 in 12 h corresponding to a net maximal rate of 1.1±0.3 ml H2/h. In contrast, in experiments with GF rats, less than 0.13 ml H2 were detectable within 12 h. The technique presented is a useful tool for studying bacterial H2 metabolism in vivo under gnotobiotic conditions.
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Ipkawati, Nelda, Saktioto Saktioto, and Saktioto Saktioto. "PENENTUAN DENSITAS PLASMA HIDROGEN NONTERMAL PADA TEKANAN RENDAH." Komunikasi Fisika Indonesia 16, no. 1 (2019): 29. http://dx.doi.org/10.31258/jkfi.16.1.29-34.
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Before producing hydrogen plasma low pressure in experiment, it is necessary to know the density equilibrium process through a simulation. Hydrogen species densities of non-thermal plasma at low pressure is simulated using chemical kinetik model by Runge Kutta method. This simulation carried out to determine the equilibrium process of densities and reaction rates of hydrogen species in achieving equilibrium conditions. The equation used time-dependent continuity equation and Arrhenius form. The hydrogen species consist of electrons, H, H2, H+ and H2+. The results of show that electron density, H, H2, H+ and H2+ are respectively 1020,23m-3, 1019,69m-3, 1019,91m-3, 1019,39m-3 and 1018,43m-3 during of 23-24 ns. These describe that the density of each species of hydrogen very fast to achieve equilibrium conditions, while the value of the reaction rate obtained can be concluded that the value of the largest reaction rate is the impact ionization process with a value of 9.86x1052m-3 s-1and the smallest one is dissociation process with a value of 1.22x10-5m-3 s-1.
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Moreno, Mario, Arturo Ponce, Arturo Galindo, et al. "Comparative Study on the Quality of Microcrystalline and Epitaxial Silicon Films Produced by PECVD Using Identical SiF4 Based Process Conditions." Materials 14, no. 22 (2021): 6947. http://dx.doi.org/10.3390/ma14226947.
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Hydrogenated microcrystalline silicon (µc-Si:H) and epitaxial silicon (epi-Si) films have been produced from SiF4, H2 and Ar mixtures by plasma enhanced chemical vapor deposition (PECVD) at 200 °C. Here, both films were produced using identical deposition conditions, to determine if the conditions for producing µc-Si with the largest crystalline fraction (XC), will also result in epi-Si films that encompass the best quality and largest crystalline silicon (c-Si) fraction. Both characteristics are of importance for the development of thin film transistors (TFTs), thin film solar cells and novel 3D devices since epi-Si films can be grown or etched in a selective manner. Therefore, we have distinguished that the H2/SiF4 ratio affects the XC of µc-Si, the c-Si fraction in epi-Si films, and the structure of the epi-Si/c-Si interface. Raman and UV-Vis ellipsometry were used to evaluate the crystalline volume fraction (Xc) and composition of the deposited layers, while the structure of the films were inspected by high resolution transmission electron microscopy (HRTEM). Notably, the conditions for producing µc-Si with the largest XC are different in comparison to the fabrication conditions of epi-Si films with the best quality and largest c-Si fraction.
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Tao, Y., D. Liu, X. Yan, Z. Zhou, J. K. Lee, and C. Yang. "Network Identification and Flux Quantification of Glucose Metabolism in Rhodobacter sphaeroides under Photoheterotrophic H2-Producing Conditions." Journal of Bacteriology 194, no. 2 (2011): 274–83. http://dx.doi.org/10.1128/jb.05624-11.
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Ponce, Angel L. G., and Jose J. Fripiat. "Interaction between atomic hydrogen and YBa2Cu3O7." Journal of Materials Research 7, no. 11 (1992): 2908–15. http://dx.doi.org/10.1557/jmr.1992.2908.
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Atomic hydrogen obtained from dissociative chemisorption of molecular H2 on Pt particles deposited on the surface of YBa2Cu3O7 reacts with the oxide in producing O vacancies and intercalating H at 82 °C under a H2 pressure of about 400 Torr. An induction period which extends over 1 h is observed as long as the concentration in O vacancies is below 0.1. Above this approximate limit the reaction proceeds quickly until about 1 mol H2 has been consumed. It then slows down progressively, but it is not completed even after 27 h of reaction and ∼1.4 H2 consumed, under these experimental conditions. The enthalpy for the creation of the O vacancy is 143 kcal/g mol O, while the H intercalation enthalpy is −57.5 kcal/g mol H. It appears that the reaction of molecular H2 over YBa2Cu3O7 not coated with Pt proceeds similarly, but the rate is nearly one order of magnitude slower, under identical conditions. The stoichiometry of the reaction agrees with the earlier suggestion that O1 is a labile oxygen which can be replaced by intercalated H. This site and the interstitial vacant sites in the copper chains square plane would be the first ones to be occupied by intercalated H.
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Hu, Jin-Shuang, Yan-Yan Huang, Jia-Hua Kuang, Jia-Jia Yu, Qin-Yu Zhou, and Dong-Mei Liu. "Streptococcus thermophiles DMST-H2 Promotes Recovery in Mice with Antibiotic-Associated Diarrhea." Microorganisms 8, no. 11 (2020): 1650. http://dx.doi.org/10.3390/microorganisms8111650.
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Antibiotic-associated diarrhea (AAD) is the most common side effect of antibiotics and is routinely treated with probiotics in clinical. Streptococcus thermophiles, extensively utilized for producing dairy foods, has recently been regarded as a new promising probiotic candidate. In this study, the efficacy of Streptococcus thermophiles DMST-H2 (DMST-H2) for AAD treatment in mice was investigated. DMST-H2 was isolated from Chinese traditional yogurt, proved to be non-toxic, and presented tolerance against simulated gastrointestinal conditions in vitro. Additionally, genomic analysis revealed that it possessed genes related to acid tolerance, bile salt tolerance, adhesion, oxidative stress and bacteriocin production. The animal experiment results showed that both DMST-H2 treatment and natural recovery could reduce fecal water content. Compared with spontaneous recovery, DMST-H2 accelerated the recovery of the enlarged caecum and intestinal barrier injury from AAD, and further decreased endotoxin (ET), D-lactate (D-LA) and diamine oxidase (DAO) content in serum. Moreover, pro-inflammatory cytokines (TNF-α) were reduced, while interferon-γ (IFN-γ) and anti-inflammatory cytokines (IL-10) increased after treating with DMST-H2. Furthermore, DMST-H2 better restored the structure of intestinal flora. At the phylum level, Firmicutes increased and Proteobacteria decreased. These findings indicate that DMST-H2 could promote recovery in mice with antibiotic-associated diarrhea.
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Kubo, Miwako, Ryota Mano, Misako Kojima та ін. "Hydrogen Selective SiCH Inorganic–Organic Hybrid/γ-Al2O3 Composite Membranes". Membranes 10, № 10 (2020): 258. http://dx.doi.org/10.3390/membranes10100258.
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Solar hydrogen production via the photoelectrochemical water-splitting reaction is attractive as one of the environmental-friendly approaches for producing H2. Since the reaction simultaneously generates H2 and O2, this method requires immediate H2 recovery from the syngas including O2 under high-humidity conditions around 50 °C. In this study, a supported mesoporous γ-Al2O3 membrane was modified with allyl-hydrido-polycarbosilane as a preceramic polymer and subsequently heat-treated in Ar to deliver a ternary SiCH organic–inorganic hybrid/γ-Al2O3 composite membrane. Relations between the polymer/hybrid conversion temperature, hydrophobicity, and H2 affinity of the polymer-derived SiCH hybrids were studied to functionalize the composite membranes as H2-selective under saturated water vapor partial pressure at 50 °C. As a result, the composite membranes synthesized at temperatures as low as 300–500 °C showed a H2 permeance of 1.0–4.3 × 10−7 mol m−2 s−1 Pa−1 with a H2/N2 selectivity of 6.0–11.3 under a mixed H2-N2 (2:1) feed gas flow. Further modification by the 120 °C-melt impregnation of low molecular weight polycarbosilane successfully improved the H2-permselectivity of the 500 °C-synthesized composite membrane by maintaining the H2 permeance combined with improved H2/N2 selectivity as 3.5 × 10−7 mol m−2 s−1 Pa−1 with 36. These results revealed a great potential of the polymer-derived SiCH hybrids as novel hydrophobic membranes for purification of solar hydrogen.
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Oyama, S. Ted, Haruki Aono, Atsushi Takagaki, Takashi Sugawara, and Ryuji Kikuchi. "Synthesis of Silica Membranes by Chemical Vapor Deposition Using a Dimethyldimethoxysilane Precursor." Membranes 10, no. 3 (2020): 50. http://dx.doi.org/10.3390/membranes10030050.
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Silica-based membranes prepared by chemical vapor deposition of tetraethylorthosilicate (TEOS) on γ-alumina overlayers are known to be effective for hydrogen separation and are attractive for membrane reactor applications for hydrogen-producing reactions. In this study, the synthesis of the membranes was improved by simplifying the deposition of the intermediate γ-alumina layers and by using the precursor, dimethyldimethoxysilane (DMDMOS). In the placement of the γ-alumina layers, earlier work in our laboratory employed four to five dipping-calcining cycles of boehmite sol precursors to produce high H2 selectivities, but this took considerable time. In the present study, only two cycles were needed, even for a macro-porous support, through the use of finer boehmite precursor particle sizes. Using the simplified fabrication process, silica-alumina composite membranes with H2 permeance > 10−7 mol m−2 s−1 Pa−1 and H2/N2 selectivity >100 were successfully synthesized. In addition, the use of the silica precursor, DMDMOS, further improved the H2 permeance without compromising the H2/N2 selectivity. Pure DMDMOS membranes proved to be unstable against hydrothermal conditions, but the addition of aluminum tri-sec-butoxide (ATSB) improved the stability just like for conventional TEOS membranes.
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Fakhroueian, Zahra, N. Afroukhteh Langroudi, Pouriya Esmaeilzadeh, et al. "The Consideration of Splendid Increasing Trend of Green Fuel H2 Production with the Help of Nanofine Materials." Defect and Diffusion Forum 297-301 (April 2010): 351–58. http://dx.doi.org/10.4028/www.scientific.net/ddf.297-301.351.
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Processes to transform natural gas into hydrogen or synthesis of gas (H2+CO) have been extensively studied in recent decades. H2 can be used in fuel cells as a power source and syngas may be converted into hydrocarbons via the Fischer-Tropsch synthesis. An attractive alternative process for syngas production is the partial oxidation of methane (POM). The objective of this study is to find effective conditions in using of nanofine particles for producing high activity and novel nanocatalysts to syngas, especially selectivity green fuel H2 gas as a power source. Therefore, we could produce 98.6% methane conversion, and 97.1% H2 selectivity with the help of unique stable and new nanofine materials: Eco-friendly x%Ni / SiO2, Co /Ce/ZrO2, Ru / Ce / ZrO2, and highly active Co-Ru and Ni-Ru bimetallic over Ce-ZrO2 nanosized mixed oxide support catalysts. Recently, we prepared new and interesting nanostructures by Cu and Ni sputtering on the nanosized Ce-ZrO2 solid solution support in the first time. Several surfactants, dispersants and mixture of alcohol solvents were applied in synthesis of nanostructures and nanofluids as remarkable templates.
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Sekoai, Patrick T., Viren Chunilall, Bruce Sithole, et al. "Elucidating the Role of Biofilm-Forming Microbial Communities in Fermentative Biohydrogen Process: An Overview." Microorganisms 10, no. 10 (2022): 1924. http://dx.doi.org/10.3390/microorganisms10101924.
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Amongst the biofuels described in the literature, biohydrogen has gained heightened attention over the past decade due to its remarkable properties. Biohydrogen is a renewable form of H2 that can be produced under ambient conditions and at a low cost from biomass residues. Innovative approaches are continuously being applied to overcome the low process yields and pave the way for its scalability. Since the process primarily depends on the biohydrogen-producing bacteria, there is a need to acquire in-depth knowledge about the ecology of the various assemblages participating in the process, establishing effective bioaugmentation methods. This work provides an overview of the biofilm-forming communities during H2 production by mixed cultures and the synergistic associations established by certain species during H2 production. The strategies that enhance the growth of biofilms within the H2 reactors are also discussed. A short section is also included, explaining techniques used for examining and studying these biofilm structures. The work concludes with some suggestions that could lead to breakthroughs in this area of research.
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Colleran, S., and S. Pender. "Mesophilic and thermophilic anaerobic digestion of sulphate-containing wastewaters." Water Science and Technology 45, no. 10 (2002): 231–35. http://dx.doi.org/10.2166/wst.2002.0339.
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The effect of sulphate at an influent chemical oxygen demand (COD):sulphate ratio of 4 on the operational performance of anaerobic hybrid reactors treating molasses wastewater was investigated under mesophilic and thermophilic conditions in a long-term laboratory-scale study over a 1,081 day period. The presence of sulphate reduced the COD removal efficiency under both mesophilic and thermophilic conditions. At 55°C, effluent acetate levels were consistently greater than 4000 mg L−1, indicating that thermophilic acetate-utilising methane-producing bacteria (MPB) or sulphate-reducing bacteria (SRB) had not developed in the reactor under the conditions applied. At 37°C, acetate was exclusively utilised by acetoclastic methanogens, whereas H2-utilising SRB predominated over H2-utilising MPB in the competition for hydrogen. By contrast, hydrogenotrophic MPB were shown to outcompete H2-utilising SRB during long-term thermophilic operation. 16SrDNA analysis of the seed sludge and reactor biomass on conclusion of the 37°C and 55°C trials illustrated that the dominant methanogen present on conclusion of the thermophilic trial in the absence of influent sulphate was related to Methanocorpusculum parvuum, and was capable of growth on both acetate and hydrogen. By contrast, an organism closely related to Methanobacterium thermoautotrophicum was the dominant methanogen present in the sulphate-fed reactor on completion of the thermophilic trial.
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Wai, SoeHtet, Yasuyuki Ota, Masakazu Sugiyama, and Kensuke Nishioka. "Evaluation of a Sabatier Reaction Utilizing Hydrogen Produced by Concentrator Photovoltaic Modules under Outdoor Conditions." Applied Sciences 10, no. 9 (2020): 3144. http://dx.doi.org/10.3390/app10093144.
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Power to gas (P2G) process chains have tremendous potential to enhance energy systems because of the capability of solar energy to convert solar radiation into electrical energy as well as the increasing use of specific gases as a means to store the resulting energy. Utilizing sunlight, photovoltaic systems are capable of producing useful gases such as hydrogen (H2) and methane (CH4). These gases are utilized in gas grids, transportation, and heavy industry. In employing a sunlight-derived gas, H2 production, by water disbanding, needs to be cost-effective with tremendous adaptability. New powerful solar to gas conversion system modules have been successfully carried out in the University of Miyazaki, Japan. These systems contain DC/DC converters and electrolyzer sets linked in parallel with efficient three concentrator photovoltaics (CPV). The performance of the solar to methane conversion process and power consumption analysis will be the focus of the current research. Efficiencies of 97.6% of CO2 to CH4 conversion and 13.8% for solar to methane on a clear sunny day were obtained by utilizing highly efficient CPV modules connected with multiple converters, electrochemical cells, and reactors fixed with Ni-based catalysts.
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Fatmi, Dini, Admin Alif, and Hamzar Suyani. "PEMECAHAN (SPLITTING) MOLEKUL AIR MENJADI GAS H2DAN O2 MELALUI PROSES FOTOVOLTAIK." Jurnal Riset Kimia 5, no. 2 (2012): 107. http://dx.doi.org/10.25077/jrk.v5i2.209.
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One method to overcome the scarcity of alternative sources of energy on earth is through the development of photovoltaic cells. This method used a solar energy to electrical energy transformation. In this research, breaking (splitting) of water molecules into H2 and O2 gas by the photovoltaic process uses electrodes CuO/C with Na2SO4 electrolyte. In this process used 2 photovoltaic cells as electricity producing and U-shaped electrolysis cell for solver (splitting) of water molecule produce H2 and O2 gas. CuO electrode (anode) is made through the burning of copper rod in a furnace at temperature 400 oC with a variety of combustion 1, 3, 4 times each lasting for 1 hs, while the cathode in the form of carbon rods obtained from 2B pencil. The optimum conditions for Na2SO4 electrolyte concentration is 0.8 N and for CuO electrodes with 3x burning. Optimum efficiency photovoltaic process was 2.66%. H2 and O2 gas volume obtained near stoichiometric ratio is 2 : 1.
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Walter, S., S. Laukenmann, A. J. M. Stams, M. K. Vollmer, G. Gleixner, and T. Röckmann. "The stable isotopic signature of biologically produced molecular hydrogen (H<sub>2</sub>)." Biogeosciences Discussions 8, no. 6 (2011): 12521–41. http://dx.doi.org/10.5194/bgd-8-12521-2011.
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Abstract. Biologically produced molecular hydrogen (H2) is characterized by a very strong depletion in deuterium. Although the biological source to the atmosphere is small compared to photochemical or combustion sources, it makes an important contribution to the global isotope budget of molecular hydrogen (H2). Large uncertainties exist in the quantification of the individual production and degradation processes that contribute to the atmospheric budget, and isotope measurements are a tool to distinguish the contributions from the different sources. Measurements of δD from the various H2 sources are scarce and for biologically produced H2 only very few measurements exist. Here the first systematic study of the isotopic composition of biologically produced H2 is presented. We investigated δD of H2 produced in a biogas plant, covering different treatments of biogas production, and from several H2 producing microorganisms such as bacteria or green algae. A Keeling plot analysis provides a robust overall source signature of δD = –712‰ (±13‰) for the samples from the biogas reactor (at 38 °C, δDH2O = 73.4‰), with a fractionation constant &amp;varepsilon;H2−H2O of –689‰ (±20‰). The pure culture samples from different microorganisms give a mean source signature of δD = –728‰ (±39‰), and a fractionation constant &amp;varepsilon;H2−H2O of –711‰ (±45‰) between H2 and the water, respectively. The results confirm the massive deuterium depletion of biologically produced H2 as was predicted by calculation of the thermodynamic fractionation factors for hydrogen exchange between H2 and water vapor. As expected for a thermodynamic equilibrium, the fractionation factor is largely independent of the substrates used and the H2 production conditions. The predicted equilibrium fractionation coefficient is positively correlated with temperature and we measured a change of 2.2‰/°C between 45 °C and 60 °C. This is in general agreement with the theoretical predictions. Our best estimate for &amp;varepsilon;H2−H2O at a temperature of 20 °C is –728‰ for biologically produced H2, and we suggest using this value in future global H2 isotope budget calculations and models.
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Tamburic, Bojan, Fessehaye W. Zemichael, Geoffrey C. Maitland, and Klaus Hellgardt. "Effect of the Light Regime and Phototrophic Conditions on Growth of the H2-producing Green Alga Chlamydomonas Reinhardtii." Energy Procedia 29 (2012): 710–19. http://dx.doi.org/10.1016/j.egypro.2012.09.083.
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Wüst, Pia K., Marcus A. Horn, and Harold L. Drake. "In Situ Hydrogen and Nitrous Oxide as Indicators of Concomitant Fermentation and Denitrification in the Alimentary Canal of the Earthworm Lumbricus terrestris." Applied and Environmental Microbiology 75, no. 7 (2009): 1852–59. http://dx.doi.org/10.1128/aem.02745-08.
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ABSTRACT The earthworm gut is a unique microzone in aerated soils that has been proposed to selectively stimulate ingested soil microorganisms by its in situ conditions, which include anoxia, high water content, a near-neutral pH, and high concentrations of organic compounds. The central objective of this study was to resolve potential links between in situ conditions and anaerobic microbial activities during the gut passage of Lumbricus terrestris. Both H2 and N2O were emitted by living earthworms, and in situ microsensor analyses revealed both H2 and N2O in the O2-free gut center. The highest H2 concentrations occurred in foregut and midgut regions, whereas the highest N2O concentrations occurred in crop/gizzard and hindgut regions. Thus, H2-producing fermentations were more localized in the foregut and midgut, whereas denitrification was more localized in the crop/gizzard and hindgut. Moisture content, total carbon, and total nitrogen were highest in the foregut and decreased from the anterior to posterior end of the gut. Nitrite, ammonium, and iron(II) concentrations were highest in the crop/gizzard and decreased from the anterior to posterior end of the alimentary canal. Concentrations of soluble organic compounds were indicative of distinct fermentation processes along the alimentary canal, with maximal concentrations of organic acids (e.g., acetate and butyrate) occurring in the midgut. These findings suggest that earthworms (i) contribute to the terrestrial cycling of carbon and nitrogen via anaerobic microbial activities in the alimentary canal and (ii) constitute a mobile source of reductant (i.e., emitted H2) for microbiota in aerated soils.
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Shiba, Nothando C., Xinying Liu, Diane Hildebrandt, and Yali Yao. "Effect of Pre-Treatment Conditions on the Activity and Selectivity of Cobalt-Based Catalysts for CO Hydrogenation." Reactions 2, no. 3 (2021): 258–74. http://dx.doi.org/10.3390/reactions2030016.
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We investigated the effect of pre-treatment conditions on the activity and selectivity of cobalt catalysts for Fischer–Tropsch synthesis (FTS) by varying both the reduction atmosphere and the reduction temperature. Catalysts supported on SiO2, Al2O3, and TiO2, prepared via incipient wetness impregnation, were evaluated, and activation temperatures in the range 250–350 °C were considered. Activation with syngas led to a better product selectivity (low CH4, high selectivity to liquid hydrocarbons, and low paraffin to olefin ratio (P/O)) than the catalysts reduced in H2 at lower activation temperatures. The CoxC species suppressed the hydrogenation reaction, and it is hypothesised that this resulted in the high selectivity of olefins observed for the syngas pre-treated catalysts. On the basis of the experimental results, we postulated that a synergistic effect between Co0 and CoxC promotes the production of the long chain hydrocarbons and suppresses the formation of CH4. In addition, for systems aimed at producing lower olefins, syngas activation is recommended, and for the FTS plants that focus on maximising the production of higher molecular weight products, H2 activation might be considered. These results provide insights for the future FTS catalyst design and for target product-driven operations.
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Chen, Hanyu, Xi Wang, Zhixiang Pan, and Hongming Xu. "Numerical Simulation and Experimental Study on Commercial Diesel Reforming Over an Advanced Pt/Rh Three-Way Catalyst." Catalysts 9, no. 7 (2019): 590. http://dx.doi.org/10.3390/catal9070590.
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Hydrocarbon fuel reforming has been proven useful for producing hydrogen that is utilized on road vehicles, but it is associated with reaction mechanism and catalyst characterization. In this study, a reduced mechanism for n-heptane/toluene reforming over an advanced Pt/Rh TWC is adopted to investigate the effects of the reaction conditions on H2 and CO concentrations. The physical and chemical properties of the advanced catalyst are examined using SEM, XRD and XPS analyses. The contrasted experiments are conducted to study the composition variation tendency of the reforming reactor gas product. The results show that the POX reaction is most likely to occur considering the stoichiometric ratio of H2/CO, and other reactions are SR or ATR. The coke formation and carbon deposition occur on the catalyst surface, and the diffraction peaks corresponding to the metallic Pt are observed, while no obvious peaks characteristic of Rh are detected. The characteristics of the concentration trend of n-heptane/toluene reforming can represent H2 and CO yield features of diesel reforming in a way; nevertheless, the difference of the average H2 and CO concentration is remarkable.
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Mukhopadhyay, Sumita, Debajyoti Das, and Swati Ray. "Better control over the onset of microcrystallinity in fast-growing silicon network." Journal of Materials Research 19, no. 9 (2004): 2597–603. http://dx.doi.org/10.1557/jmr.2004.0338.
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In view of obtaining a Si:H network at the onset of microcrystallinity at a high deposition rate, we have adopted an intelligent approach to find out a tricky plasma condition in radio frequency (rf) plasma-enhanced chemical vapordeposition that provides a better control on growth introducing retarded microcrystallization. The deposition parameter includes a combination of high electrical power applied to the (SiH4+H2)-plasma and high gas pressure in thereaction chamber. High rf power increases the number density of film-forming precursors as well as atomic H density in the plasma, which helps to increase thefilm deposition rate and to promote microcrystallinity, respectively. In addition,high pressure helps not only to increase the film-growth rate by producing a dense plasma but also retards the microcrystallization process by increasing significantlythe gas phase collision frequency and consequently reducing the effective reactivityof atomic H on the surface of a fast-growing Si:H network. A combination of high-power and high-pressure plasma conditions provides a reasonably wide rangeof H2 dilution to work with and better control in producing a Si:H network at theonset of microcrystallinity, while increasing the film-growth rate.
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Sangsong, Suntorn, Tanakorn Ratana, Sabaithip Tungkamani, Thana Sornchamni, Monrudee Phongaksorn, and Eric Croiset. "The Demonstration of the Superiority of the Dual Ni-Based Catalytic System for the Adjustment of the H2/CO Ratio in Syngas for Green Fuel Technologies." Catalysts 10, no. 9 (2020): 1056. http://dx.doi.org/10.3390/catal10091056.
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A novel dual Ni-based catalytic process (DCP) to control the H2/CO ratio of 2 in the syngas product within one step at temperature <700 °C was created and constructed. With the sequence of the catalysts located in the single reactor, the endothermic combined steam and CO2 reforming of methane (CSCRM) reaction and the exothermic ultra-high-temperature water–gas shift (UHT-WGS) reaction work continuously. During the process, the H2/CO ratio is raised suddenly at UHT-WGS after the syngas is produced from CSCRM, and CSCRM utilizes the heat released from UHT-WGS. Due to these features, DCP is more compact, enhances energy efficiency, and thus decreases the capital cost compared to reformers connecting with shift reactors. To prove this propose, the DCP tests were done in a fixed-bed reactor under various conditions (temperature = 500, 550, and 600 °C; the feed mixture (CH4, CO2, H2O, and N2) with H2O/(CH4 + CO2) ratio = 0.33, 0.53, and 0.67). According to the highest CH4 conversion (around 65%) with carbon tolerance, the recommended conditions for producing syngas with the H2/CO ratio of 2 as a feedstock of Fischer–Tropsch synthesis include the temperature of 600 °C and the H2O/(CH4 + CO2) ratio of 0.53.
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Lang, Susan Q., Marvin D. Lilley, Tamara Baumberger, et al. "Extensive decentralized hydrogen export from the Atlantis Massif." Geology 49, no. 7 (2021): 851–56. http://dx.doi.org/10.1130/g48322.1.
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Abstract Hydrogen is an important energy source for subsurface microbial communities, but its availability beyond the flow focused through hydrothermal chimneys is largely unknown. We report the widespread export of H2 across the Atlantis Massif oceanic core complex (30°N, Mid-Atlantic Ridge; up to 44 nM), which is distinct from the circulation system feeding the Lost City Hydrothermal Field (LCHF) on the massif's southern wall. Methane (CH4) abundances are generally low to undetectable (&lt;3 nM) in fluids that are not derived from the LCHF. Reducing fluids exit the seafloor over a wide geographical area and depth range, including the summit of the massif and along steep areas of mass wasting east of the field. The depth of the fluids in the water column and their H2/CH4 ratios indicate that some are sourced separately from the LCHF. We argue that extensive H2 export is the natural consequence of fluid flow pathways strongly influenced by tectonic features and the volume and density changes that occur when ultramafic rocks react to form serpentinites, producing H2 as a by-product. Furthermore, the circulation of H2-rich fluids through uplifted mantle rocks at moderate temperatures provides geographically expansive and stable environmental conditions for the early evolution of biochemical pathways. These results provide insight into the spatial extent of H2- and CH4-bearing fluids associated with serpentinization, independent of the focused flow emanating from the LCHF.
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Dzul Rashidi, Nur Farahana, Nur Syakina Jamali, Siti Syazwani Mahamad, et al. "Effects of Alginate and Chitosan on Activated Carbon as Immobilisation Beads in Biohydrogen Production." Processes 8, no. 10 (2020): 1254. http://dx.doi.org/10.3390/pr8101254.
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In this study, the effects of alginate and chitosan as entrapped materials in the biofilm formation of microbial attachment on activated carbon was determined for biohydrogen production. Five different batch fermentations, consisting of mixed concentration alginate (Alg), were carried out in a bioreactor at temperature of 60 °C and pH 6.0, using granular activated carbon (GAC) as a primer for cell attachment and colonisation. It was found that the highest hydrogen production rate (HPR) of the GAC–Alg beads was 2.47 ± 0.47 mmol H2/l.h, and the H2 yield of 2.09 ± 0.22 mol H2/mol sugar was obtained at the ratio of 2 g/L of Alg concentration. Next, the effect of chitosan (C) as an external polymer layer of the GAC–Alg beads was investigated as an alternative approach to protecting the microbial population in the biofilm in a robust environment. The formation of GAC with Alg and chitosan (GAC–AlgC) beads gave the highest HPR of 0.93 ± 0.05 mmol H2/l.h, and H2 yield of 1.11 ± 0.35 mol H2/mol sugar was found at 2 g/L of C concentration. Hydrogen production using GAC-attached biofilm seems promising to achieve consistent HPRs at higher temperatures, using Alg as immobilised bead material, which has indicated a positive response in promoting the growth of hydrogen-producing bacteria and providing excellent conditions for microorganisms to grow and colonise high bacterial loads in a bioreactor.
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Wrubel, Jacob A., Jason Zack, Andrew M. Park, and Guido Bender. "Operando Measurement of Hydrogen Crossover in Proton Exchange Membrane Electrolysis Cells at Differential Pressures." ECS Meeting Abstracts MA2022-02, no. 39 (2022): 1440. http://dx.doi.org/10.1149/ma2022-02391440mtgabs.
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Low temperature water electrolysis (LTE) using proton exchange membrane electrolysis cells (PEMECs) is a promising approach for producing green H2 that can use electricity from renewable sources. In practice, H2 is stored and dispensed at high pressures. To alleviate efficiency losses associated with pressurizing the product hydrogen, PEMECs can be operated at high differential pressures, e.g., >30bar on the cathode side. However, high differential pressure operation can result in undesirable H2 crossover to the anode (O2) side. This not only reduces the Faradaic efficiency of the cell, but also can result in flammability hazards. H2 crossover in PEMECs is a function of both materials properties such as membrane thickness, water uptake, and permeability, and operating conditions such as temperature, differential pressure, and current density. Example data are shown in Figure 1. While thinner membranes are susceptible to higher H2 crossover rates, they are a desirable material to use because they can result in significantly improved cell performance and lower material and production costs. To mitigate safety concerns related to H2 crossover, gas recombination catalyst (GRC) layers can be introduced into the membrane electrode assembly. The GRCs will react the crossover H2 with O2 to produce water, thereby minimizing the amount of H2 entering the O2 stream. In this talk we will present data from operando crossover measurements of PEMECs employing a variety of membrane materials, both with and without GRCs. The experiments are complimented by modeling results that allow further insights into the processes at hand. Multiple temperatures, differential pressures, and current densities are studied. The results will investigate the tradeoff between performance and capturable H2 production that occurs when thinner membranes are used, and how this effect responds to differential pressure operation. Figure 1
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Dujjanutat, Praepilas, Arthit Neramittagapong, and Pakawadee Kaewkannetra. "Optimization of Bio-Hydrogenated Kerosene from Refined Palm Oil by Catalytic Hydrocracking." Energies 12, no. 16 (2019): 3196. http://dx.doi.org/10.3390/en12163196.
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In this work, hydro-processing was used as an alternative route for producing bio-hydrogenated kerosene (BHK) from refined bleached deodorized palm oil (RPO) in the presence of a 0.5 wt% Pd/Al2O3 catalyst. The Box-Behnken Design was used to determine the effects of reaction temperature, H2 pressure, and reaction time in terms of liquid hourly space velocity (LHSV) on BHK production. The kerosene selectivity was used as the response for staticial interpretation. The results show that both temperature and LHSV produced significant effects, whereas H2 pressure did not. The optimal conditions were found to be 483 °C, 5.0 MPa, and 1.4 h−1 LHSV; these conditions provided approximately 57.30% kerosene selectivity and a 47.46% yield. The BHK product had a good heating value and flash point. However, the mass percentage of carbon and hydrogen was 99.1%, which is just below the minimum standard (99.5%), according to the carbon loss by the reaction pathway to form as CO and CO2. Water can be produced from the reaction induced by oxygen removal, which results in a high freezing point.
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Walter, S., S. Laukenmann, A. J. M. Stams, M. K. Vollmer, G. Gleixner, and T. Röckmann. "The stable isotopic signature of biologically produced molecular hydrogen (H<sub>2</sub>)." Biogeosciences 9, no. 10 (2012): 4115–23. http://dx.doi.org/10.5194/bg-9-4115-2012.
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Abstract. Biologically produced molecular hydrogen (H2) is characterised by a very strong depletion in deuterium. Although the biological source to the atmosphere is small compared to photochemical or combustion sources, it makes an important contribution to the global isotope budget of H2. Large uncertainties exist in the quantification of the individual production and degradation processes that contribute to the atmospheric budget, and isotope measurements are a tool to distinguish the contributions from the different sources. Measurements of δ D from the various H2 sources are scarce and for biologically produced H2 only very few measurements exist. Here the first systematic study of the isotopic composition of biologically produced H2 is presented. In a first set of experiments, we investigated δ D of H2 produced in a biogas plant, covering different treatments of biogas production. In a second set of experiments, we investigated pure cultures of several H2 producing microorganisms such as bacteria or green algae. A Keeling plot analysis provides a robust overall source signature of δ D = −712‰ (±13‰) for the samples from the biogas reactor (at 38 °C, δ DH2O= +73.4‰), with a fractionation constant &amp;varepsilon;H2-H2O of −689‰ (±20‰) between H2 and the water. The five experiments using pure culture samples from different microorganisms give a mean source signature of δ D = −728‰ (±28‰), and a fractionation constant &amp;varepsilon;H2-H2O of −711‰ (±34‰) between H2 and the water. The results confirm the massive deuterium depletion of biologically produced H2 as was predicted by the calculation of the thermodynamic fractionation factors for hydrogen exchange between H2 and water vapour. Systematic errors in the isotope scale are difficult to assess in the absence of international standards for δ D of H2. As expected for a thermodynamic equilibrium, the fractionation factor is temperature dependent, but largely independent of the substrates used and the H2 production conditions. The equilibrium fractionation coefficient is positively correlated with temperature and we measured a rate of change of 2.3‰ / °C between 45 °C and 60 °C, which is in general agreement with the theoretical prediction of 1.4‰ / °C. Our best experimental estimate for &amp;varepsilon;H2-H2O at a temperature of 20 °C is −731‰ (±20‰) for biologically produced H2. This value is close to the predicted value of −722‰, and we suggest using these values in future global H2 isotope budget calculations and models with adjusting to regional temperatures for calculating δ D values.
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Ye, Feng, Shuanshi Fan, Wenjun Li, et al. "Simultaneous Production of Aromatics and COx-Free Hydrogen via Methane Dehydroaromatization in Membrane Reactors: A Simulation Study." Membranes 12, no. 12 (2022): 1175. http://dx.doi.org/10.3390/membranes12121175.
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As an alternative route for aromatics and hydrogen production, methane dehydroaromatization (MDA) is of significant academic and industrial interest due to the abundance of natural gas resources and the intensive demand for aromatics and COx-free hydrogen. In the present work, a simulation study on MDA in membrane reactors (MRs) was performed with the aim of co-producing aromatics and COx-free hydrogen with a highly improved efficiency. The effects of various parameters, including catalytic activity, membrane flux and selectivity, as well as the operating conditions on the MR performance were discussed with respect to methane conversion, hydrogen yield, and hydrogen purity. The results show that catalytic activity and membrane flux and selectivity have significant impacts on CH4 conversion and H2 yield, whereas H2 purity is mainly dominated by membrane selectivity. A highly improved MDA is confirmed to be feasible at a relatively low temperature and a high feed pressure because of the hydrogen extraction effect. To further improve MDA in MRs by intensifying H2 extraction, a simple configuration combining a fixed-bed reactor (FBR) and an MR together is proposed for MDA, which demonstrates good potential for the high-efficiency co-production of aromatics and COx-free hydrogen.
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Al-Mubaddel, Fahad, Samsudeen Kasim, Ahmed A. Ibrahim, Abdulrhman S. Al-Awadi, Anis H. Fakeeha, and Ahmed S. Al-Fatesh. "H2 Production from Catalytic Methane Decomposition Using Fe/x-ZrO2 and Fe-Ni/(x-ZrO2) (x = 0, La2O3, WO3) Catalysts." Catalysts 10, no. 7 (2020): 793. http://dx.doi.org/10.3390/catal10070793.
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An environmentally-benign way of producing hydrogen is methane decomposition. This study focused on methane decomposition using Fe and Fe-Ni catalysts, which were dispersed over different supports by the wet-impregnation method. We observed the effect of modifying ZrO2 with La2O3 and WO3 in terms of H2 yield and carbon deposits. The modification led to a higher H2 yield in all cases and WO3-modified support gave the highest yield of about 90% and was stable throughout the reaction period. The reaction conditions were at 1 atm, 800 °C, and 4000 mL(hgcat)−1 space velocity. Adding Ni to Fe/x-ZrO2 gave a higher H2 yield and stability for ZrO2 and La2O3 + ZrO2-supported catalysts whose prior performances and stabilities were very poor. Catalyst samples were analyzed by characterization techniques like X-ray diffraction (XRD), nitrogen physisorption, temperature-programmed reduction (TPR), thermo-gravimetric analysis (TGA), and Raman spectroscopy. The phases of iron and the supports were identified using XRD while the BET revealed a significant decrease in the specific surface areas of fresh catalysts relative to supports. A progressive change in Fe’s oxidation state from Fe3+ to Fe0 was observed from the H2-TPR results. The carbon deposits on Fe/ZrO2 and Fe/La2O3 + ZrO2 are mainly amorphous, while Fe/WO3 + ZrO2 and Fe-Ni/x-ZrO2 are characterized by graphitic carbon.
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Pohorelic, Brant K. J., Johanna K. Voordouw, Elisabeth Lojou, Alain Dolla, Jens Harder, and Gerrit Voordouw. "Effects of Deletion of Genes Encoding Fe-Only Hydrogenase of Desulfovibrio vulgaris Hildenborough on Hydrogen and Lactate Metabolism." Journal of Bacteriology 184, no. 3 (2002): 679–86. http://dx.doi.org/10.1128/jb.184.3.679-686.2002.
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ABSTRACT The physiological properties of a hyd mutant of Desulfovibrio vulgaris Hildenborough, lacking periplasmic Fe-only hydrogenase, have been compared with those of the wild-type strain. Fe-only hydrogenase is the main hydrogenase of D. vulgaris Hildenborough, which also has periplasmic NiFe- and NiFeSe-hydrogenases. The hyd mutant grew less well than the wild-type strain in media with sulfate as the electron acceptor and H2 as the sole electron donor, especially at a high sulfate concentration. Although the hyd mutation had little effect on growth with lactate as the electron donor for sulfate reduction when H2 was also present, growth in lactate- and sulfate-containing media lacking H2 was less efficient. The hyd mutant produced, transiently, significant amounts of H2 under these conditions, which were eventually all used for sulfate reduction. The results do not confirm the essential role proposed elsewhere for Fe-only hydrogenase as a hydrogen-producing enzyme in lactate metabolism (W. A. M. van den Berg, W. M. A. M. van Dongen, and C. Veeger, J. Bacteriol. 173:3688–3694, 1991). This role is more likely played by a membrane-bound, cytoplasmic Ech-hydrogenase homolog, which is indicated by the D. vulgaris genome sequence. The physiological role of periplasmic Fe-only hydrogenase is hydrogen uptake, both when hydrogen is and when lactate is the electron donor for sulfate reduction.
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Nesse, Live L., Camilla Sekse, Kristin Berg, et al. "Potentially Pathogenic Escherichia coli Can Form a Biofilm under Conditions Relevant to the Food Production Chain." Applied and Environmental Microbiology 80, no. 7 (2013): 2042–49. http://dx.doi.org/10.1128/aem.03331-13.
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ABSTRACTThe biofilm-producing abilities of potentially human-pathogenic serotypes ofEscherichia colifrom the ovine reservoir were studied at different temperatures and on different surfaces. A possible influence of the hydrophobicity of the bacterial cells, as well as the presence of two virulence factors, the Shiga toxin-encoding (Stx) bacteriophage and theeaegene, was also studied. A total of 99E. coliisolates of serotypes O26:H11, O103:H2, and O103:H25 isolated from sheep feces were included. The results show that isolates of all threeE. coliserotypes investigated can produce biofilm on stainless steel, glass, and polystyrene at 12, 20, and 37°C. There was a good general correlation between the results obtained on the different surfaces.E. coliO103:H2 isolates produced much more biofilm than those of the other two serotypes at all three temperatures. In addition, isolates of serotype O26:H11 produced more biofilm than those of O103:H25 at 37°C. The hydrophobicity of the isolates varied between serotypes and was also influenced by temperature. The results strongly indicated that hydrophobicity influenced the attachment of the bacteria rather than their ability to form biofilm once attached. Isolates with theeaegene produced less biofilm at 37°C than isolates without this gene. The presence of a Stx bacteriophage did not influence biofilm production. In conclusion, our results show that potentially human-pathogenicE. colifrom the ovine reservoir can form biofilm on various surfaces and at several temperatures relevant for food production and handling.
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Gabriel, André, Alison F. Nogueira, Douglas M. Zeffa, et al. "Productivity, physicochemical quality and early flowering resistance of experimental onion hybrids." Horticultura Brasileira 40, no. 2 (2022): 197–207. http://dx.doi.org/10.1590/s0102-0536-20220209.
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ABSTRACT In order to produce bulbs or seeds, onion plants depend on genotype X environment interaction. Thus, breeders shall select the genotypes based on the climatic conditions of each producing region. This study aimed to evaluate 17 experimental onion hybrids and two commercial genotypes (‘Bella Dura’ and ‘Buccaneer’), based on agronomic, physicochemical attributes of the bulbs and resistance to early flowering under subtropical conditions. Joint analysis of variance and phenotypic divergence estimated through principal component analysis (PCA) and Ward’s hierarchical clustering were performed. We observed that the time of transplantation affected the agronomic traits more than the physicochemical traits, not affecting the percentage of early flowering of the genotypes. The first transplant season provided higher bulb productivity, whereas the second season reduced the cycle and productivity. Hybrids H1, H17 and ‘Buccaneer’ showed flowering rate lower than 3%. Among the experimental hybrids, H2 showed higher productivity when comparing with commercial cultivars, and H1, H12 and H14 were equivalent to them. However, H12 showed the highest early flowering rate (43%). Thus, considering the experimental genotypes evaluated under subtropical conditions, H1, H2, and H14, showed potential for commercial use or as potential parents in advancing the breeding program, as they stood out for presenting good yield, bulb quality and low percentage of early flowering.
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Sokolova, Tatyana G., Nadezhda A. Kostrikina, Nikolai A. Chernyh, Tatjana V. Kolganova, Tatjana P. Tourova, and Elizaveta A. Bonch-Osmolovskaya. "Thermincola carboxydiphila gen. nov., sp. nov., a novel anaerobic, carboxydotrophic, hydrogenogenic bacterium from a hot spring of the Lake Baikal area." International Journal of Systematic and Evolutionary Microbiology 55, no. 5 (2005): 2069–73. http://dx.doi.org/10.1099/ijs.0.63299-0.
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A novel anaerobic, thermophilic, alkalitolerant bacterium, strain 2204T, was isolated from a hot spring of the Baikal Lake region. The cells of strain 2204T were straight rods of variable length, Gram-positive with an S-layer, motile with one to two lateral flagella, and often formed aggregates of 3–15 cells. The isolate was shown to be an obligate anaerobe oxidizing CO and producing equimolar quantities of H2 and CO2 according to the equation CO+H2O→CO2+H2. No organic substrates were used as energy sources. For lithotrophic growth on CO, 0·2 g acetate or yeast extract l−1 was required but did not support growth in the absence of CO. Growth was observed in the temperature range 37–68 °C, the optimum being 55 °C. The pH range for growth was 6·7–9·5, the optimum pH being 8·0. The generation time under optimal conditions was 1·3 h. The DNA G+C content was 45 mol%. Penicillin, erythromycin, streptomycin, rifampicin, vancomycin and tetracycline completely inhibited both growth and CO utilization by strain 2204T. Thus, isolate 2204T was found to be the first known moderately thermophilic and alkalitolerant H2-producing anaerobic carboxydotroph. The novel bacterium fell within the cluster of the family Peptococcaceae within the low-G+C-content Gram-positive bacteria, where it formed a separate branch. On the basis of morphological, physiological and phylogenetic features, strain 2204T should be assigned to a novel genus and species, for which the name Thermincola carboxydiphila gen. nov., sp. nov. is proposed. The type strain is strain 2204T (=DSM 17129T=VKM B-2283T=JCM 13258T).
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Novikov, Andrey A., Tatyana G. Sokolova, Alexander V. Lebedinsky, Tatyana V. Kolganova, and Elizaveta A. Bonch-Osmolovskaya. "Carboxydothermus islandicus sp. nov., a thermophilic, hydrogenogenic, carboxydotrophic bacterium isolated from a hot spring." International Journal of Systematic and Evolutionary Microbiology 61, no. 10 (2011): 2532–37. http://dx.doi.org/10.1099/ijs.0.030288-0.
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An anaerobic, thermophilic bacterium, strain SET IS-9T, was isolated from an Icelandic hot spring. Cells of strain SET IS-9T are short, slightly curved, motile rods. The strain grows chemolithotrophically on CO, producing equimolar quantities of H2 and CO2. It also grows fermentatively on lactate or pyruvate in the presence of yeast extract (0.2 g l−1). Products of pyruvate fermentation are acetate, CO2 and H2. Growth occurs at 50–70 °C, with an optimum at 65 °C, and at pH 5.0–8.0, with an optimum at pH 5.5–6.0. The generation time during chemolithotrophic growth on CO under optimal conditions is 2.0 h. 16S rRNA gene sequence analysis suggested that the organism belongs to the genus Carboxydothermus. On the basis of phenotypic features and phylogenetic analysis, Carboxydothermus islandicus sp. nov. is proposed, with the type strain SET IS-9T ( = DSM 21830T = VKM B-2561T). An emended description of the genus Carboxydothermus is also given.
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Slepova, Tatiana V., Tatyana G. Sokolova, Anatoly M. Lysenko, et al. "Carboxydocella sporoproducens sp. nov., a novel anaerobic CO-utilizing/H2-producing thermophilic bacterium from a Kamchatka hot spring." International Journal of Systematic and Evolutionary Microbiology 56, no. 4 (2006): 797–800. http://dx.doi.org/10.1099/ijs.0.63961-0.
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A novel anaerobic, thermophilic, CO-utilizing bacterium, strain KarT, was isolated from a hot spring of Karymskoe Lake, Kamchatka Peninsula. The cells of the novel isolate were Gram-positive, spore-forming, short rods. The bacterium grew chemolithoautotrophically on CO, producing equimolar quantities of H2 and CO2 (according to the equation CO + H2O → CO2 + H2), and in the absence of CO, under N2 in the gas phase, chemoorganoheterotrophically with yeast extract, sucrose or pyruvate. Growth was observed in the temperature range 50–70 °C, with an optimum at 60 °C, and in the pH range 6·2–8·0, with an optimum at pH 6·8. The micro-organism did not grow on solid media; it was able to grow only in semi-solid medium containing 0·5 % agar. The generation time under optimal conditions for chemolithoautotrophic growth was 1 h. The G+C content of the DNA was 46·5±1 mol%. Growth was completely inhibited by penicillin, novobiocin, streptomycin, kanamycin and neomycin. Analysis of the 16S rRNA gene sequence showed that the isolate should be assigned to the genus Carboxydocella. On the basis of the results of DNA–DNA hybridization and morphological and physiological analyses, strain KarT represents a novel species of the genus Carboxydocella, for which the name Carboxydocella sporoproducens sp. nov. is proposed. The type strain is KarT (=DSM 16521T=VKM B-2358T).
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Yip, Terence, Kai-Chung Tse, Man-Fai Lam, et al. "Risk Factors and Outcomes of Extended-Spectrum Beta-Lactamase-Producing E. Coli Peritonitis in Capd Patients." Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis 26, no. 2 (2006): 191–97. http://dx.doi.org/10.1177/089686080602600213.
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Objective To determine the risk factors and outcomes of peritonitis caused by extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in continuous ambulatory peritoneal dialysis (CAPD). Patients and Methods Episodes of E. coli CAPD peritonitis in our unit from October 1994 to August 2003 were reviewed. Demographic data, underlying medical conditions, recent use of gastric acid inhibitors (including H2 antagonist and proton pump inhibitor), recent antibiotic therapy, antibiotic regimen for peritonitis episodes, sensitivity test results of the E. coli isolated, and clinical outcomes were examined. Results Over a 10-year study period, 88 episodes of E. coli peritonitis were recorded; 11 of the 88 cases were caused by ESBL-producing E. coli. Recent use of cephalosporins and gastric acid inhibitor were associated with the development of ESBL-producing E. coli peritonitis. Compared with non-ESBL-producing E. coli peritonitis, more cases in the ESBL-producing E. coli group developed treatment failure (45.5% vs 13.0%, p = 0.02) and died of sepsis (27.3% vs 3.9%, p = 0.02). Peritoneal failure rate was higher in the ESBL-producing E. coli group, although the difference was not statistically significant (18.2% vs 3.9%, p = 0.12). Conclusion Peritonitis caused by ESBL-producing E. coli is associated with worse clinical outcomes. The use of cephalosporins and gastric acid inhibitors may contribute to its development. Further studies are warranted to investigate and determine the predisposing factors for ESBL-producing E. coli peritonitis.
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Falabella Sousa-Aguiar, Eduardo, Carolina Zanon Costa, Maria Antonieta Peixoto Gimenes Couto, Débora de Almeida Azevedo, and José Faustino Souza de Carvalho Filho. "Conversion of Residual Palm Oil into Green Diesel and Biokerosene Fuels under Sub- and Supercritical Conditions Employing Raney Nickel as Catalyst." Catalysts 11, no. 8 (2021): 995. http://dx.doi.org/10.3390/catal11080995.
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A comprehensive study of the thermal deoxygenation of palm residue under sub- and supercritical water conditions using Raney nickel as a heterogeneous catalyst is presented in this paper. Hydrothermal technology was chosen to replace the need for hydrogen as a reactant, as happens, for example, in catalytic hydrotreatment. Several experiments were carried out at different reaction temperatures (350, 370, and 390 °C) and were analyzed with different times of reaction (1, 3.5, and 6 h) and catalyst loads (5, 7.5, 10 wt.%). No hydrogen was introduced in the reactions, but it was produced in situ. The results showed the selectivity of biokerosene ranged from 2% to 67%, and the selectivity of diesel ranged from 5% to 98%. The best result was achieved for 390 °C, 10 wt.% catalyst load, and 3.5 h of reaction, when the selectivities equal to 67% for biokerosene and 98% for diesel were obtained. The Raney nickel catalyst demonstrated a tendency to promote the decarboxylation reaction and/or decarbonylation reaction over the hydrodeoxygenation reaction. Moreover, the fatty acid and glycerol reforming reaction and the water−gas shift reaction were the main reactions for the in situ H2 generation. This study demonstrated that a hydrothermal catalytic process is a promising approach for producing liquid paraffin (C11−C17) from palm residue under the conditions of no H2 supply.
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Klimenko, V. M., and T. T. Suprun. "METHANATION TECHNOLOGIES FOR PRODUCING SYNTHETIC RENEWABLE METHANE." Thermophysics and Thermal Power Engineering 46, no. 3 (2022): 63–72. http://dx.doi.org/10.31472/ttpe.3.2022.6.
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Methanation, or the generation of synthetic methane through the combination of carbon dioxide and hydrogen, has been attracting more and more attention of researchers and energy scientists in recent years due to the fact that the development of an effective and economically feasible technology for the implementation of this process will allow solving a number of energy and environmental problems. First, it is the accumulation of excess renewable electricity from solar and wind power plants by using it in the creation of another energy-intensive product, namely synthetic natural gas, which removes the problem of coordinating unstable sources of electricity with energy networks. Secondly, methanation becomes another technology for enriching biogas and turning it into biomethane, which will allow it to be used through existing gas networks and contribute to solving the problem of natural gas shortage.
 The development and improvement of methanation technologies are engaged in many organizations of the world - Germany, Denmark, France, the USA, Japan and others. Research is conducted in two main directions: catalytic methanation and biological methanation. In the first direction, methanation is carried out through the Sabatier reaction using catalysts. The problems of such methanation are: the development of catalysts with high activity, selectivity and resistance to the heat of reaction, the provision of optimal reaction modes, in particular temperature and pressure, through the use of various methods of reactor cooling, control of the reaction mechanism, the use of three-phase reactors, changing their structure, and so on. Biological methanation is carried out using of biological methanogens - so-called archaea, which act as a kind of catalyst. The methanation is carried out either directly in the biomass anaerobic digestion reactor (in-situ methanation) or in a separate reactor into which biogas and hydrogen are fed separately (ex-situ methanation). One of the main problems of in-situ methanation is the simultaneous provision of optimal conditions for both acetoclastic and hydrogenotrophic methanogens. This problem is solved by ex-situ methanation, in which the optimal conditions for anaerobic digestion and methanation processes are provided separately. It is clear that optimal conditions are also provided for biomethanation of pure CO2 and H2, when the «broth» for archaea is created separately. A comparison of catalytic and biological methanation technologies shows that catalytic methanation provides higher energy efficiency and requires much smaller reactor sizes than biological methanation for the same methane yield. However, the latter has a higher resistance to harmful impurities than the catalytic one.
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Tommasi, T., G. Sassi, and B. Ruggeri. "Acid pre-treatment of sewage anaerobic sludge to increase hydrogen producing bacteria HPB: effectiveness and reproducibility." Water Science and Technology 58, no. 8 (2008): 1623–28. http://dx.doi.org/10.2166/wst.2008.506.
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The present study is aimed to test the effectiveness and the reproducibility of the acid pre-treatment of sewage sludge to suppress the methanogenic bacteria activity, in order to increase the hydrogen forming bacteria activity, mainly Clostridium species. The treated sludge has been tested on glucose reach medium under mesophilic conditions (35°C), in batch mode to quantify the biological fermentative hydrogen production. In the whole series of experiments, the main components of biogas are hydrogen (52–60%) and carbon dioxide (40–48%); no methane and hydrogen sulphide were present in it. The rate of biogas production reached a maximum of 75 ml/lh. An overall mean hydrogen conversion efficiency was 11.20% on the assumption of maximum of 3 mol H2/mol glucose. Clostridium spp. multiplied ten times after 10 h of fermentation and over that thousand times at the end of fermentation.
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Rodríguez-Reyes, Juan José, Octavio García-Depraect, Roberto Castro-Muñoz, and Elizabeth León-Becerril. "Dark Fermentation Process Response to the Use of Undiluted Tequila Vinasse without Nutrient Supplementation." Sustainability 13, no. 19 (2021): 11034. http://dx.doi.org/10.3390/su131911034.
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The technical feasibility of valorizing tequila vinasse (TV), a wastewater with high pollution potential, through the production of biogenic hydrogen via dark fermentation, has long been proven in diverse lab-scale reactors that were operated either in batch or continuous mode. However, such systems have mainly been tested with diluted streams and nutrient supplementation, hindering the techno-economic attractiveness of the TV-to-hydrogen concept at large scale. In this study, the feasibility of producing hydrogen from high-strength undiluted TV with no added extra nutrients was evaluated under batch mesophilic conditions. Additionally, the use of two different acidogenic inocula obtained either by heat or heat-aeration pretreatment was investigated to get a greater understanding of the effect of inoculum type on the process. The results obtained showed that the TV utilized herein contained macro- and micro-nutrients high enough to support the hydrogenogenic activity of both cultures, entailing average hydrogen yields of 2.4–2.6 NL H2/L vinasse and maximum hydrogen production rates of 1.4–1.9 NL H2/L-d. Interestingly, the consumption of lactate and acetate with the concomitant production of butyrate was observed as the main hydrogen-producing route regardless of the inoculum, pointing out the relevance of the lactate-driven dark fermentative process. Clostridium beijerinckii was ascertained as key bacteria, but only in association with microorganisms belonging to the genera Enterobacter and Klebsiella, as revealed by phylogenetic analyses.
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Hayakawa, Kayoko, Sureka Gattu, Dror Marchaim та ін. "Epidemiology and Risk Factors for Isolation of Escherichia coli Producing CTX-M-Type Extended-Spectrum β-Lactamase in a Large U.S. Medical Center". Antimicrobial Agents and Chemotherapy 57, № 8 (2013): 4010–18. http://dx.doi.org/10.1128/aac.02516-12.
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ABSTRACTA case-case-control study was conducted to identify independent risk factors for recovery ofEscherichia colistrains producing CTX-M-type extended-spectrum β-lactamases (CTX-ME. coli) within a large Southeastern Michigan medical center. Unique cases with isolation of ESBL-producingE. colifrom February 2010 through July 2011 were analyzed by PCR forblaCTX-M,blaTEM, andblaSHVgenes. Patients with CTX-ME. coliwere compared to patients withE. colistrains not producing CTX-M-type ESBLs (non-CTX-ME. coli) and uninfected controls. Of 575 patients with ESBL-producingE. coli, 491 (85.4%) isolates contained a CTX-M ESBL gene. A total of 319 (84.6%) patients with CTX-ME. coli(282 [74.8%] CTX-M-15 type) were compared to 58 (15.4%) non-CTX-ME. colipatients and to uninfected controls. Independent risk factors for CTX-ME. coliisolation compared to non-CTX-ME. coliincluded male gender, impaired consciousness, H2 blocker use, immunosuppression, and exposure to penicillins and/or trimethoprim-sulfamethoxazole. Compared to uninfected controls, independent risk factors for isolation of CTX-ME. coliincluded presence of a urinary catheter, previous urinary tract infection, exposure to oxyimino-cephalosporins, dependent functional status, non-home residence, and multiple comorbid conditions. Within 48 h of admission, community-acquired CTX-ME. coli(n= 51 [16%]) and non-CTX-ME coli(n= 11 [19%]) strains were isolated from patients with no recent health care contacts. CTX-ME. colistrains were more resistant to multiple antibiotics than non-CTX-ME. colistrains. CTX-M-encoding genes, especiallyblaCTX-M-15type, represented the most common ESBL determinants from ESBL-producingE. coli, the majority of which were present upon admission. Septic patients with risk factors for isolation of CTX-ME. colishould be empirically treated with appropriate agents. Regional infection control efforts and judicious antibiotic use are needed to control the spread of these organisms.
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Imizcoz, Mikel, and Alberto V. Puga. "Assessment of Photocatalytic Hydrogen Production from Biomass or Wastewaters Depending on the Metal Co-Catalyst and Its Deposition Method on TiO2." Catalysts 9, no. 7 (2019): 584. http://dx.doi.org/10.3390/catal9070584.
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A systematic study on the solar photocatalytic hydrogen production (photoreforming) performance of M/TiO2 (M = Au, Ag, Cu or Pt) using glucose as a model substrate, and further extended to lignocellulose hydrolysates and wastewaters, is herein presented. Three metal (M) co-catalyst loading methods were tested. Variation of the type of metal results in significantly dissimilar H2 production rates, albeit the loading method exerts an even greater effect in most cases. Deposition-precipitation (followed by hydrogenation) or photodeposition provided better results than classical impregnation (followed by calcination). Interestingly, copper as a co-catalyst performed satisfactorily as compared to Au, and slightly below Pt, thus representing a realistic inexpensive alternative to noble metals. Hydrolysates of either α-cellulose or rice husks, obtained under mild conditions (short thermal cycles at 160 °C), were rich in saccharides and thus suitable as feedstocks. Nonetheless, the presence of inhibiting byproducts hindered H2 production. A novel photocatalytic UV pre-treatment method was successful to initially remove the most recalcitrant portion of these minor products along with H2 production (17 µmol gcat−1 h−1 on Cu/TiO2). After a short UV step, simulated sunlight photoreforming was orders of magnitude more efficient than without the pre-treatment. Hydrogen production was also directly tested on two different wastewater streams, that is, a municipal influent and samples from operations in a fruit juice producing plant, with remarkable results obtained for the latter (up to 115 µmol gcat−1 h−1 using Au/TiO2).
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Senko, Olga, Olga Maslova, Marina Gladchenko, et al. "Prospective Approach to the Anaerobic Bioconversion of Benzo- and Dibenzothiophene Sulfones to Sulfide." Molecules 24, no. 9 (2019): 1736. http://dx.doi.org/10.3390/molecules24091736.
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Sulfur recovery from organic molecules such as toxic sulfones is an actual problem, and its solution through the use of environmentally friendly and nature-like processes looks attractive for research and application. For the first time, the possible bioconversion of organic sulfones (benzo-and dibenzothiophene sulfones) to inorganic sulfide under anaerobic conditions with simultaneous biogas production from glucose within a methanogenesis process is demonstrated. Biogas with a methane content of 50.7%–82.1% was obtained without H2S impurities. Methanogenesis with 99.7%–100% efficiency and 97.8%–100% conversion of benzo- and dibenzothiophene sulfones (up to 0.45 mM) to inorganic sulfide were obtained in eight days by using a combination of various anaerobic biocatalysts immobilized in a poly(vinyl alcohol) cryogel. Pure cell cultures of sulfate-reducing bacteria and/or H2-producing bacteria were tested as additives to the methanogenic activated sludge. The immobilized activated sludge “enhanced” by bacterial additives appeared to retain its properties and be usable multiple times for the conversion of sulfones under batch conditions.
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Sawamura, Okamoto, and Todokoro. "Development of Mass Production Technology of Highly Permeable Nano-Porous Supports for Silica-Based Separation Membranes." Membranes 9, no. 8 (2019): 103. http://dx.doi.org/10.3390/membranes9080103.
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Silica-based membranes show both robust properties and high-permeability, offering us great potential for applying them to harsh conditions where conventional organic membranes cannot work. Despite the increasing number of paper and patents of silica-based membranes, their industrial applications have yet to be fully realized, possibly due to their lack of technologies on scaling-up and mass production. In particular, quality of membrane supports decisively impacts final quality of silica-based separation membranes. In this study, therefore, we have developed mass producing technologies of nano-porous supports (φ 12 mm, length 400 mm) with surface center pore size distribution of 1–10 nm, which are generally used as supports for preparing separation membranes with a pore size of less than 1 nm. The developed mass production apparatuses have enabled us to reproducibly produce nano-porous silica-based supports with high permeance (e.g., N2 permeance of more than 10−5 mol m−2 s−1·Pa−1) minimizing effects of membrane defects less than 0.1% of the total flux. The developed nano-porous supports have enabled us to reproducibly produce silica-based separation membranes with high permeace and selectivity (e.g., H2 permeance of about 5 × 10−6 mol m−2 s−1 Pa−1 and H2/SF6 permeance ratio of more than 2000).