Artigos de revistas: "ChitosanNP"

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KIM, KYUNG W., R. L. THOMAS, CHAN LEE e HYUN J. PARK. "Antimicrobial Activity of Native Chitosan, Degraded Chitosan, and O-Carboxymethylated Chitosan". Journal of Food Protection 66, n.º 8 (1 de agosto de 2003): 1495–98. http://dx.doi.org/10.4315/0362-028x-66.8.1495.

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The antimicrobial activity of native chitosan was compared to that of lipase-degradedchitosan. The effects of O-carboxymethylated (O-CM) substitution on native (molecular weight, 120; degree of deacetylation, 84.71%) and lipase-degraded chitosans were also investigated. The antimicrobial activity of native chitosan was more extensive than that of lipase-degraded chitosan; however, lipase-degraded chitosan was still highly effective and more water-soluble. O-CM chitosan derived from degraded chitosan was more effective than O-CM chitosan derived from native chitosan. O-CM substitution enhanced lipase-degraded chitosan's antimicrobial activity without reducing its solubility.

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Khayrova, Adelya, Sergey Lopatin, Balzhima Shagdarova, Olga Sinitsyna, Arkady Sinitsyn e Valery Varlamov. "Evaluation of Antibacterial and Antifungal Properties of Low Molecular Weight Chitosan Extracted from Hermetia illucens Relative to Crab Chitosan". Molecules 27, n.º 2 (17 de janeiro de 2022): 577. http://dx.doi.org/10.3390/molecules27020577.

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This study shows the research on the depolymerisation of insect and crab chitosans using novel enzymes. Enzyme preparations containing recombinant chitinase Chi 418 from Trichoderma harzianum, chitinase Chi 403, and chitosanase Chi 402 from Myceliophthora thermophila, all belonging to the family GH18 of glycosyl hydrolases, were used to depolymerise a biopolymer, resulting in a range of chitosans with average molecular weights (Mw) of 6–21 kDa. The depolymerised chitosans obtained from crustaceans and insects were studied, and their antibacterial and antifungal properties were evaluated. The results proved the significance of the chitosan’s origin, showing the potential of Hermetia illucens as a new source of low molecular weight chitosan with an improved biological activity.

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Malm, Morgan, e Andrea M. Liceaga. "Physicochemical Properties of Chitosan from Two Commonly Reared Edible Cricket Species, and Its Application as a Hypolipidemic and Antimicrobial Agent". Polysaccharides 2, n.º 2 (12 de maio de 2021): 339–53. http://dx.doi.org/10.3390/polysaccharides2020022.

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Insect-derived chitin and chitosan have gained interest as alternative sources to that derived from crustaceans; however, little information is available on chitin from the house cricket (Acheta domesticus) and tropical banded cricket (Gryllodes sigillatus), two cricket species commonly reared in the United States for human consumption. In this study, chitin was successfully isolated and purified from these two cricket species; using FTIR, chitins were found to be in alpha-crystalline form. Cricket chitosan was produced from both species with varying degrees of deacetylation (DDA) by varying alkaline conversion duration. G. sigillatus chitosan was larger (524 kDa) than A. domesticus chitosan (344 kDa). Both cricket chitosans showed similar (p > 0.05) lipid-binding capacity to that of shrimp chitosan. Both chitosans were as effective at inhibiting microbial growth of surrogate foodborne pathogens as the commercial shrimp chitosan. At a concentration of 0.50 mg/mL cricket chitosan, approximately 100% of Listeria innocua growth was inhibited, due to a contribution of both chitosan and the solvent-acetic acid. At the same concentration, growth of Escherichia coli was inhibited 90% by both cricket chitosan samples with ~80% DDA, where a decrease in the DDA led to decreased antimicrobial activity. However, varying the DDA had no effect on chitosan’s lipid-binding capacity. As more edible insects become a normalized protein source in our diet, the use of by-products, such as chitin and chitosan, derived from insect protein processing, show promising applications for the pharmaceutical and food industries.

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Derwich, Marcin, Lukasz Lassmann, Katarzyna Machut, Agata Zoltowska e Elzbieta Pawlowska. "General Characteristics, Biomedical and Dental Application, and Usage of Chitosan in the Treatment of Temporomandibular Joint Disorders: A Narrative Review". Pharmaceutics 14, n.º 2 (27 de janeiro de 2022): 305. http://dx.doi.org/10.3390/pharmaceutics14020305.

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The aim of this narrative review was to present research investigating chitosan, including its general characteristics, properties, and medical and dental applications, and finally to present the current state of knowledge regarding the efficacy of chitosan in the treatment of temporomandibular disorders (TMDs) based on the literature. The PICO approach was used for the literature search strategy. The PubMed database was analyzed with the following keywords: (“chitosan”[MeSH Terms] OR “chitosan”[All Fields] OR “chitosans”[All Fields] OR “chitosan s”[All Fields] OR “chitosane”[All Fields]) AND (“temporomandibular joint”[MeSH Terms] OR (“tem-poromandibular”[All Fields] AND “joint”[All Fields]) OR “temporomandibular joint”[All Fields] OR (“temporomandibular”[All Fields] AND “joints”[All Fields]) OR “temporo-mandibular joints”[All Fields]). After screening 8 results, 5 studies were included in this review. Chitosan presents many biological properties and therefore it can be widely used in several branches of medicine and dentistry. Chitosan promotes wound healing, helps to control bleeding, and is used in wound dressings, such as sutures and artificial skin. Apart from its antibacterial property, chitosan has many other properties, such as antifungal, mucoadhesive, anti-inflammatory, analgesic, antioxidant, antihyperglycemic, and antitumoral properties. Further clinical studies assessing the efficacy of chitosan in the treatment of TMD are required. According to only one clinical study, chitosan was effective in the treatment of TMD; however, better clinical results were obtained with platelet-rich plasma.

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Wang, Hezhong, e Maren Roman. "Effects of Chitosan Molecular Weight and Degree of Deacetylation on Chitosan−Cellulose Nanocrystal Complexes and Their Formation". Molecules 28, n.º 3 (31 de janeiro de 2023): 1361. http://dx.doi.org/10.3390/molecules28031361.

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This study was conducted to determine the effects of chitosan molecular weight and degree of deacetylation (DD) on chitosan–cellulose nanocrystal (CNC) polyelectrolyte–macroion complexes (PMCs) and their formation. Chitosan samples with three different molecular weights (81, 3 · 103, 6 · 103 kDa) and four different DDs (77, 80, 85, 89%) were used. The effects on PMC formation were determined by turbidimetric titration. An effect of the molecular weight of chitosan was not observed in turbidimetric titrations. Turbidity levels were higher for CNCs with lower sulfate group density and larger hydrodynamic diameter than for CNCs with higher sulfate group density and smaller hydrodynamic diameter. Conversely, turbidity levels were higher for chitosans with higher DD (higher charge density) than for chitosans with lower DD (lower charge density). PMC particles from chitosans with different molecular weights were characterized by scanning electron microscopy, laser Doppler electrophoresis, and dynamic light scattering. PMCs from high-molecular-weight chitosan were more spherical and those from medium-molecular-weight chitosan had a slightly larger hydrodynamic diameter than PMCs from the respective other two chitosans. The molecular weight of the chitosan was concluded to have no effect on the formation of chitosan–CNC PMC particles and only a minor effect on the shape and size of the particles. The higher turbidity levels for CNCs with lower sulfate group density and larger hydrodynamic diameter and for chitosans with higher DD were attributed to a larger number of CNCs being required for charge compensation.

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Lončarević, Andrea, Karla Ostojić, Inga Urlić e Anamarija Rogina. "Preparation and Properties of Bimetallic Chitosan Spherical Microgels". Polymers 15, n.º 6 (16 de março de 2023): 1480. http://dx.doi.org/10.3390/polym15061480.

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The aim of this work was to prepare bimetallic chitosan microgels with high sphericity and investigate the influences of metal-ion type and content on the size, morphology, swelling, degradation and biological properties of microgels. Amino and hydroxyl groups of chitosan (deacetylation degree, DD, of 83.2% and 96.9%) served as ligands in the Cu2+–Zn2+/chitosan complexes with various contents of cupric and zinc ions. The electrohydrodynamic atomization process was used to produce highly spherical microgels with a narrow size distribution and with surface morphology changing from wrinkled to smooth by increasing Cu2+ ions’ quantity in bimetallic systems for both used chitosans. The size of the bimetallic chitosan particles was estimated to be between 60 and 110 µm for both used chitosans, and FTIR spectroscopy indicated the formation of complexes through physical interactions between the chitosans’ functional groups and metal ions. The swelling capacity of bimetallic chitosan particles decreases as the DD and copper (II) ion content increase as a result of stronger complexation with respect to zinc (II) ions. Bimetallic chitosan microgels showed good stability during four weeks of enzymatic degradation, and bimetallic systems with smaller amounts of Cu2+ ions showed good cytocompatibility for both used chitosans.

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Jaidee, A., Pornchai Rachtanapun e S. Luangkamin. "¹H-NMR Analysis of Degree of Substitution in N,O-Carboxymethyl Chitosans from Various Chitosan Sources and Types". Advanced Materials Research 506 (abril de 2012): 158–61. http://dx.doi.org/10.4028/www.scientific.net/amr.506.158.

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N,O-Carboxymethyl chitosans were synthesized by the reaction between shrimp, crab and squid chitosans with monochloroacetic acid under basic conditions at 50°C. The mole ratio of reactants was obtained from various reaction conditions of shrimp chitosan polymer and oligomer types. The mole ratio 1:12:6 of chitosan:sodium hydroxide:monochloroacetic acid was used for preparing carboxymethyl of chitosan polymer types while carboxymethyl of chitosan oligomer types were used the mole ratio 1:6:3 of chitosan:sodium hydroxide:monochloroacetic acid. The chemical structure was analyzed by fourier transformed infrared spectroscopy (FT-IR) and proton nuclear magnatic resonance spectroscopy (1H-NMR). The FT-IR was used for confirm the insertion of carboxymethyl group on chitosan molecules. The 1H-NMR was used for determining the degree of substitution (DS) of carboxymethylation at hydroxyl and amino sites of chitosans. Carboxymethyl chitosan samples had the total DS of carboxymethylation ranging from 1.0-2.2. The highest of DS of carboxymethylation was from shrimp chitosan oligomer type.

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Ortega-Ortiz, Hortensia, Baltazar Gutiérrez-Rodríguez, Gregorio Cadenas-Pliego e Luis Ibarra Jimenez. "Antibacterial activity of chitosan and the interpolyelectrolyte complexes of poly(acrylic acid)-chitosan". Brazilian Archives of Biology and Technology 53, n.º 3 (junho de 2010): 623–28. http://dx.doi.org/10.1590/s1516-89132010000300016.

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The antimicrobial activity of chitosan and water soluble interpolyelectrolyte complexes of poly(acrylic acid)-chitosan was studied. Chitosans of two different molecular weights were tested at different concentration for 0.5 to 5 g·L-1 as antimicrobial agents against P. aeruginosa and P. oleovorans. In both cases, the best microbial inhibition was obtained with the concentration of 5 g·L-1. However, the interpolyelectrolyte complexes of poly(acrylic acid)-chitosan with composition φ =2 produced higher antibacterial activity than the two chitosans at the concentration of 0.5 g·L-1. The NPEC2 complex was more effective than chitosans. This could be attributed to the number of moles of the amino groups of chitosan and the carboxylic acid groups of the interpolyelectrolyte complexes poly(acrylic acid).

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Coquery, Clément, Claire Negrell, Nicolas Caussé, Nadine Pébère e Ghislain David. "Synthesis of new high molecular weight phosphorylated chitosans for improving corrosion protection". Pure and Applied Chemistry 91, n.º 3 (26 de março de 2019): 509–21. http://dx.doi.org/10.1515/pac-2018-0509.

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Abstract Two grades of chitosan [chitosan 30000 g mol−1 (N-chitosan 30) and 250000 g mol−1 (N-chitosan 250)] were functionalized by the Kabachnik–Fields reaction. To obtain the highest phosphonic ester grafting rate (55% and 40% for the N-chitosan 30 and N-chitosan 250, respectively), the pH must be kept constant during the reaction (pH=5). Then, a partial hydrolysis of the ester functions was carried out in HCl medium to generate phosphonic acid functions up to 25% and 20% for the N-chitosan 30 and N-chitosan 250, respectively. It was shown that the grafting of phosphonic acids on chitosan significantly reduced the dynamic viscosity. Afterwards, electrochemical impedance measurements were performed in an aqueous solution (pH=5) in the presence of either N-chitosans or P-chitosans (3 wt.%). The two native N-chitosans were little adsorbed onto the carbon steel surface and the corrosion protection was low. In contrast, the impedance results in the presence of the 30000 g mol−1 phosphorylated chitosan (P-chitosan 30) evidenced the beneficial effect of grafted phosphonic acid on its adsorption on the steel surface. The lower efficiency of the 250000 g mol−1 (P-chitosan 250) was attributed to its high molecular weight which made difficult the interactions between the phosphonic groups and the metallic surface.

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Mati-Baouche, Narimane, Cédric Delattre, Hélène de Baynast, Michel Grédiac, Jean-Denis Mathias, Alina Violeta Ursu, Jacques Desbrières e Philippe Michaud. "Alkyl-Chitosan-Based Adhesive: Water Resistance Improvement". Molecules 24, n.º 10 (23 de maio de 2019): 1987. http://dx.doi.org/10.3390/molecules24101987.

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A chemical modification by grafting alkyl chains using an octanal (C8) on chitosan was conducted with the aim to improve its water resistance for bonding applications. The chemical structure of the modified polymers was determined by NMR analyses revealing two alkylation degrees (10 and 15%). In this study, the flow properties of alkyl-chitosans were also evaluated. An increase in the viscosity was observed in alkyl-chitosan solutions compared with solutions of the same concentration based on native chitosan. Moreover, the evaluation of the adhesive strength (bond strength and shear stress) of both native and alkyl-chitosans was performed on two different double-lap adherends (aluminum and wood). Alkyl-chitosans (10 and 15%) maintain sufficient adhesive properties on wood and exhibit better water resistance compared to native chitosan.

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Pokhrel, Shanta, Ralf Lach, Wolfgang Grellmann, Andre Wutzler, Werner Lebek, Reinhold Godehardt, Paras Nath Yadav e Rameshwar Adhikari. "Synthesis of Chitosan from Prawn Shells and Characterization of its Structural and Antimicrobial Properties". Nepal Journal of Science and Technology 17, n.º 1 (31 de julho de 2016): 5–9. http://dx.doi.org/10.3126/njst.v17i1.25056.

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Chitin was prepared from prawn shells waste by chemical treatments viz. demineralization, deproteinization and decolorization. Chitosan was prepared by deacetylation of chitin with 50% NaOH at 100 °C in the presence of nitrogen. Deacetylation was performed at different intervals of time to get a series of chitosans having different degrees of deacetylation. Prepared chitosans were characterized by molecular weight determination, degree of deacetylation, Fourier transform infrared (FTIR) spectroscopy and Scanning electron micrography (SEM). The degree of deacetylation of chitosans was calculated by acid base titration and potentiometric titration. The molecular weights of commercial and prepared chitosan (CS-4.0) samples were determined using the Mark- Houwink equation and were found to be 3.5 × 105 (g/mole) and 3.3 × 104 (g/mole), respectively. The degree of deacetylation was found to linearly increase with the increase of reaction time. FTIR spectra showed the characteristic peaks of chitin and chitosan. Antimicrobial screening results revealed that the prepared chitosan (CS-4.0) was equally or more biologically active than the commercial chitosan.

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Fu, Ran Ran, Xiu Jie Ji, Yan Fei Ren, Gang Wang e Bo Wen Cheng. "Different Molecular Weight Chitosans Prepared via the Ionic Liquid Hydrolysis and their Antibacterial Activity". Key Engineering Materials 730 (fevereiro de 2017): 127–34. http://dx.doi.org/10.4028/www.scientific.net/kem.730.127.

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The hydrolysis effect of ionic liquid glycine chloride [Gly]Cl aqueous system without any catalyst on the degradation for chitosan were studied. The molecular weight (Mw) and degree of deacetylation (DD) of degraded products were tested via the viscometric method and the titration method, respectively. The structure of the raw and degraded chitosans were assessed through Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). Besides, the antibacterial effects of different Mw chitosans to Escherichia coli and Staphylococcus aureus were evaluated. The results showed that [Gly]Cl aqueous solution was of good assistant degradation effect for chitosan and different molecular weight (300-800 kDa) chitosans were obtained with different processing time via the ionic liquid hydrolysis method. The DD of degraded chitosans tested from titration method was almost unchanged by the treatment. The FTIR and XRD results showed that the ionic liquid degradation had no obvious effect on the molecular structure of chitosan. Besides, the antibacterial activity was closely relevant to the chitosan concentration and Mw. When the concentration was greater than 0.005% (w/v), chitosan began to show strong antibacterial activity. Molecular weight of 636 kDa exhibited commendable antimicrobial properties to E. coli and S. aureus simultaneously.

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Mello, Karine Gargioni Pereira Correa de, Leandra de Cássia Bernusso, Ronaldo Nogueira de Moraes Pitombo e Bronislaw Polakiewicz. "Synthesis and physicochemical characterization of chemically modified chitosan by succinic anhydride". Brazilian Archives of Biology and Technology 49, n.º 4 (julho de 2006): 665–68. http://dx.doi.org/10.1590/s1516-89132006000500017.

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The N-succinil-chitosan is a chemically modified derivative of the biopolymer chitosan. The succinic anhydride attached to the free amino groups presented along the chitosan's polymer chain imparts to the molecule different physicochemical properties not exhibited before the modification. These chemical modifications enhance chitosan's solubility in slightly acid, neutral and alkaline media. These properties are related to the long alkyl chains attached to hydrophilic parts. In this case the hydrophilic part of D-glucosamine promotes stronger interactions with the water molecules, and consequently, enhances the solubility of the chitosan polymer. Non-modified free chitosan is soluble only in acidic medium (pH < 5.5). These modifications made possible new applications of chitosan in biotechnological area since the solubility in neutral or slightly alkaline solutions is very important in a biological field.

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GANAN, M., A. V. CARRASCOSA e A. J. MARTÍNEZ-RODRÍGUEZ. "Antimicrobial Activity of Chitosan against Campylobacter spp. and Other Microorganisms and Its Mechanism of Action". Journal of Food Protection 72, n.º 8 (1 de agosto de 2009): 1735–38. http://dx.doi.org/10.4315/0362-028x-72.8.1735.

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The antimicrobial activities of three chitosans with different molecular masses against six gram-negative and three gram-positive bacteria were examined. Campylobacter spp. were the microorganisms most sensitive to chitosan, regardless of their molecular mass. The MIC of chitosan for Campylobacter ranged from 0.005 to 0.05%, demonstrating the global sensitivity of campylobacters to chitosan. Chitosan caused a loss in the membrane integrity of Campylobacter, measured as an increase in cell fluorescence due to the uptake of propidium iodide, a dye that is normally excluded from cells with intact membranes. As cells entered the stationary phase, there was a change in cell membrane resistance toward a loss of integrity caused by chitosan. This study demonstrates that chitosans could be a promising antimicrobial to control Campylobacter.

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Gomes, Laidson, Hiléia Souza, José Campiña, Cristina Andrade, António Silva, Maria Gonçalves e Vania Paschoalin. "Edible Chitosan Films and Their Nanosized Counterparts Exhibit Antimicrobial Activity and Enhanced Mechanical and Barrier Properties". Molecules 24, n.º 1 (31 de dezembro de 2018): 127. http://dx.doi.org/10.3390/molecules24010127.

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Chitosan and chitosan-nanoparticles were combined to prepare biobased and unplasticized film blends displaying antimicrobial activity. Nanosized chitosans obtained by sonication for 5, 15, or 30 min were combined with chitosan at 3:7, 1:1, and 7:3 ratios, in order to adjust blend film mechanical properties and permeability. The incorporation of nanosized chitosans led to improvements in the interfacial interaction with chitosan microfibers, positively affecting film mechanical strength and stiffness, evidenced by scanning electron microscopy. Nanosized or blend chitosan film sensitivity to moisture was significantly decreased with the drop in biocomposite molecular masses, evidenced by increased water solubility and decreased water vapor permeability. Nanosized and chitosan interactions gave rise to light biobased films presenting discrete opacity and color changes, since red-green and yellow-blue colorations were affected. All chitosan blend films exhibited antimicrobial activity against both Gram-positive and Gram-negative bacteria. The performance of green unplasticized chitosan blend films displaying diverse morphologies has, thus, been proven as a potential step towards the design of nontoxic food packaging biobased films, protecting against spoilage microorganisms, while also minimizing environmental impacts.

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Xu, Qing, Tian Zhong e Hui Li Li. "Antioxidant and Free Radical Scavenging Activities of N-Modified Chitosans". Advanced Materials Research 1002 (agosto de 2014): 91–98. http://dx.doi.org/10.4028/www.scientific.net/amr.1002.91.

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Recently, the search for effective natural antioxidants use in food and medicinal fields to replace synthetic ones has attracted the most attention. Chitosan, a natural nontoxic biopolymer, is known to possess antioxidant property, which is attributed that NH2 and OH attached in the pyranose ring react with unstable free radicals to form stable macromolecule radicals. It has been observed that the antioxidant activity of chitosan is closely related to the form of nitrogen atom in the molecules. This review focuses on the antioxidant and free radical scavenging activities of various nitrogen atom of chitosan, including N-acylated chitosans, Schiff bases of chitosan, N-alkyl chitosan, and N-quaternized chitosan. The free radical scavenging mechanisms are summarized and the effects on free radical scavenging activity of N-modified chitosan are discussed. This work may provide more insights into the antioxidant ability of N-modified chitosans and potentially enable them to be used as natural antioxidants for application in food, agriculture, cosmetic and biomedical science. Keywords: N-modified chitosan, Sythesis, Antioxidant, Free radical scavenging

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Qin, Xiaofei, Jana Emich e Francisco Goycoolea. "Assessment of the Quorum Sensing Inhibition Activity of a Non-Toxic Chitosan in an N-Acyl Homoserine Lactone (AHL)-Based Escherichia coli Biosensor". Biomolecules 8, n.º 3 (4 de setembro de 2018): 87. http://dx.doi.org/10.3390/biom8030087.

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New approaches to deal with drug-resistant pathogenic bacteria are urgent. We studied the antibacterial effect of chitosans against an Escherichia coli quorum sensing biosensor reporter strain and selected a non-toxic chitosan to evaluate its quorum sensing (QS) inhibition activity and its effect on bacterial aggregation. To this end, chitosans of varying degree of acetylation (DA) (12 to 69%) and molecular weight (Mw) (29 to 288 kDa) were studied. Only chitosans of low DA (~12%) inhibited bacterial growth, regardless of their Mw. A chitosan with medium degree of polymerization (named MDP) DA30, with experimental DA 42% and Mw 115 kDa was selected for further QS inhibition and scanning electron microscopy (SEM) imaging studies. MDP DA30 chitosan exhibited QS inhibition activity in an inverse dose-dependent manner (≤12.5 µg/mL). SEM images revealed that this chitosan, when added at low concentration (≤30.6 µg/mL), induced substantial bacterial aggregation, whereas at high concentration (234.3 µg/mL), it did not. Aggregation explains the QS inhibition activity as the consequence of retardation of the diffusion of N-acylated homoserine lactones (AHLs).

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Peker, Ismail, Faik N. Oktar, Murat Senol e M. Eroglu. "An Economic Method for Chitosan Production". Key Engineering Materials 309-311 (maio de 2006): 473–76. http://dx.doi.org/10.4028/www.scientific.net/kem.309-311.473.

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Chitosan is a deacetylated derivative of chitin, which is a naturally abundant mucopolysaccharide, supporting the matter of crustaceans, insects, and fungi. Because of its unique properties, such as non-toxicity, biodegradability, and biocompatibility, chitosan has a wide range of applications in various fields. Increasing interest on chitosan’s usage has resulted in high consumption. Therefore, production of chitosan from essential sources with desired characteristics has become an important issue. Several methods, with different chemicals and reaction conditions, have been reported in the literature. This study aimed to shed light in several features of a very promising chitin isolation method described by Tolaimate et al. and its effect on the produced chitosan’s phisico-chemical characteristics.

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Vendramin, Veronica, Gaia Spinato e Simone Vincenzi. "Shellfish Chitosan Potential in Wine Clarification". Applied Sciences 11, n.º 10 (13 de maio de 2021): 4417. http://dx.doi.org/10.3390/app11104417.

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Chitosan is a chitin-derived fiber, extracted from the shellfish shells, a by-product of the fish industry, or from fungi grown in bioreactors. In oenology, it is used for the control of Brettanomyces spp., for the prevention of ferric, copper, and protein casse and for clarification. The International Organisation of Vine and Wine established the exclusive utilization of fungal chitosan to avoid the eventuality of allergic reactions. This work focuses on the differences between two chitosan categories, fungal and animal chitosan, characterizing several samples in terms of chitin content and degree of deacetylation. In addition, different acids were used to dissolve chitosans, and their effect on viscosity and on the efficacy in wine clarification were observed. The results demonstrated that even if fungal and animal chitosans shared similar chemical properties (deacetylation degree and chitin content), they showed different viscosity depending on their molecular weight but also on the acid used to dissolve them. A significant difference was discovered on their fining properties, as animal chitosans showed a faster and greater sedimentation compared to the fungal ones, independently from the acid used for their dissolution. This suggests that physical–chemical differences in the molecular structure occur between the two chitosan categories and that this significantly affects their technologic (oenological) properties.

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Basseri, Hamidreza, Ronak Bakhtiyari, Sayed Jamal Hashemi, Mojgan Baniardelani, Hadi Shahraki e Laila Hosainpour. "Antibacterial/Antifungal Activity of Extracted Chitosan From American Cockroach (Dictyoptera: Blattidae) and German Cockroach (Blattodea: Blattellidae)". Journal of Medical Entomology 56, n.º 5 (29 de maio de 2019): 1208–14. http://dx.doi.org/10.1093/jme/tjz082.

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Abstract We investigated bactericidal and fungicidal properties of chitosan extracted from adults and nymphs from both German cockroach, Blattella germanica (Blattodea: Blattellidae) and American cockroach, Periplaneta americana (Dictyoptera: Blattidae). The cuticle of adults and nymphs extracted from both cockroaches were dried and ground. The powders were demineralized and deproteinized followed by deacetylation using NaOH. Finally, the chitosan yields were examined for antibacterial and antifungal activities. The degree of deacetylation (DD) was different between adults and nymph stages. The antimicrobial effect of American cockroach chitosan (ACC) and German cockroach chitosan (GCC) was tested against four bacteria and four fungi. The extracted chitosans from American cockroach, Periplaneta americana and German Cockroach, Blattella germanica suppressed the growth of Gram-negative/positive bacteria except Micrococcus luteus. The growth of Aspergillus flavus and Aspergillus niger were notability inhibited by the extracted chitosans. The antimicrobial effect of the chitosan depended on the cockroach species, with chitosan of the American cockroach showing more inhibitory effect. This difference may be due to differences in the structure of chitin between the two cockroach species.

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Reay, Sophie L., Emma L. Jackson, Daniel Salthouse, Ana Marina Ferreira, Catharien M. U. Hilkens e Katarina Novakovic. "Effective Endotoxin Removal from Chitosan That Preserves Chemical Structure and Improves Compatibility with Immune Cells". Polymers 15, n.º 7 (23 de março de 2023): 1592. http://dx.doi.org/10.3390/polym15071592.

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Chitosan is one of the most researched biopolymers for healthcare applications, however, being a naturally derived polymer, it is susceptible to endotoxin contamination, which elicits pro-inflammatory responses, skewing chitosan’s performance and leading to inaccurate conclusions. It is therefore critical that endotoxins are quantified and removed for in vivo use. Here, heat and mild NaOH treatment are investigated as facile endotoxin removal methods from chitosan. Both treatments effectively removed endotoxin to below the FDA limit for medical devices (<0.5 EU/mL). However, in co-culture with peripheral blood mononuclear cells (PBMCs), only NaOH-treated chitosan prevented TNF-α production. While endotoxin removal is the principal task, the preservation of chitosan’s structure is vital for the synthesis and lysozyme degradation of chitosan-based hydrogels. The chemical properties of NaOH-treated chitosan (by FTIR-ATR) were significantly similar to its native composition, whereas the heat-treated chitosan evidenced macroscopic chemical and physical changes associated with the Maillard reaction, deeming this treatment unsuitable for further applications. Degradation studies conducted with lysozyme demonstrated that the degradation rates of native and NaOH-treated chitosan-genipin hydrogels were similar. In vitro co-culture studies showed that NaOH hydrogels did not negatively affect the cell viability of monocyte-derived dendritic cells (moDCs), nor induce phenotypical maturation or pro-inflammatory cytokine release.

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Pérez-Millán, Rafael, Jose Maria Cámara-Zapata, Juan Carlos Fernández-Zapata, Silvia Simón-Grao, Marina Alfosea-Simón, Ernesto Alejandro Zavala-González, Muhammad Adnan Shahid e Francisco García-Sánchez. "Application of Biocat G, Selenium, and Chitosan to Counteract the Negative Effects of Cd in Broccoli Plants Grown in Soilless Culture". Agronomy 12, n.º 6 (30 de maio de 2022): 1327. http://dx.doi.org/10.3390/agronomy12061327.

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The accumulation of cadmium in plants produces phytotoxic damage and a decrease in crop yield. To avoid this effect, it is necessary to prevent its absorption by roots and reduce its toxicity in plant tissues. The current study was aimed to evaluate the effect of the exogenous applications of Biocat G (fulvic/humic acids), selenium (Se), and chitosan to roots and leaves of broccoli plants exposed to Cd stress. The applied treatments were: (i) T1: Hoagland nutrient solution (NS), (ii) T2: NS + Cd at 3 mg L-1 (NS + Cd), (iii) T3: NS + Cd + root application of Biocat G (NS + Cd + BioG), (iv) T4: NS + Cd + foliar application of Se (NS + Cd + Se1), (v) T5: NS + Cd + root application of Se (NS + Cd + Se2), (vi) T6: NS + Cd + foliar application of chitosan (NS + Cd + chitosan1), and (vii) T7: NS + Cd + root application of chitosan (NS + Cd + chitosan2). The results showed that the exogenous application of Biocat G and Se (T3 and T5) ameliorated the adverse effects caused by Cd toxicity and significantly improved plant growth rate by decreasing Cd toxicity; besides, Biocat G was able to limit the transport of Cd from the leaves to the inflorescences, reducing the content of Cd in the edible part. These treatments (T3 and T5) yielded the best results, act on the plants by deactivating Cd toxicity, but they did not affect its accumulation in the plant tissue. In addition, Biocat G limits the transport of Cd from the non-edible to the edible part.

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El-araby, Abir, Lahsen El Ghadraoui e Faouzi Errachidi. "Physicochemical Properties and Functional Characteristics of Ecologically Extracted Shrimp Chitosans with Different Organic Acids during Demineralization Step". Molecules 27, n.º 23 (28 de novembro de 2022): 8285. http://dx.doi.org/10.3390/molecules27238285.

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The current study aims to develop eco-friendly and economical chitosans with a wide range of applications using organic acids for shrimp shells demineralization. Chitosan samples were extracted from shrimp (Parapenaeus longirostris) shells and the demineralization step was performed with three organic acids (citric, acetic, and lactic) and two mineral acids (hydrochloric and sulfuric). The chitosans were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The chitosans’ physicochemical properties were also determined. The characteristic bands and functional groups of the chitosans were identified by FTIR spectra. The chitosans’ crystallinity order was as follows: ChHCl > ChCitric > ChH2SO4 > ChLactic > ChAcetic. The chitosans’ morphological characteristics revealed a smooth surface and fibrous structures with pores. Chitosans extracted by organic acids showed the highest extraction yields. ChHCl and ChCitric had higher degrees of deacetylation values; 83.67% and 81.47%, respectively. The solubility was proportional to the degree of deacetylation. Furthermore, ChH2SO4 and ChCitric had lower molecular weight values; 149 kDa and 183 kDa, respectively. Organic acids are as effective as mineral acids for shrimp shells demineralization. The developed process opens up possibilities to produce chitin and chitosan in a more eco-friendly way and at a lower cost in many industrial sectors.

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Lee, Dae-Sung, Sung-Hwan Eom, Young-Mog Kim, Hye Seon Kim, Mi-Jin Yim, Sang-Hoon Lee, Do-Hyung Kim e Jae-Young Je. "Antibacterial and synergic effects of gallic acid-grafted-chitosan with β-lactams against methicillin-resistant Staphylococcus aureus (MRSA)". Canadian Journal of Microbiology 60, n.º 10 (outubro de 2014): 629–38. http://dx.doi.org/10.1139/cjm-2014-0286.

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Methicillin-resistant Staphylococcus aureus (MRSA) is spreading worldwide, emphasizing the need to search for new antibiotics. The anti-MRSA activities of gallic acid-grafted-chitosans (GA-g-chitosans) were investigated against 2 MRSA standards and 10 MRSA clinical isolates by determining the minimum inhibitory concentrations (MICs). GA-g-chitosan (I), which has the highest gallic acid content, exhibited the strongest anti-MRSA activities, with MICs of 32–64 μg/mL. A time-kill investigation revealed that GA-g-chitosan (I) exhibited a bactericidal effect at twice the MIC, also demonstrating good thermal and pH stability. Investigation of cell envelope integrity showed the release of intracellular components with an increasing absorbance value at 260 nm, indicating cell envelope damage caused by the GA-g-chitosan (I), which was further confirmed by transmission electron microscopy. When GA-g-chitosans were combined with β-lactams, including ampicillin and penicillin, synergistic effects were observed on the 2 standard MRSA strains and on the 10 clinical isolates, with fractional inhibitory indices ranging from 0.125 to 0.625. In the time-kill dynamic confirmation test, synergistic bactericidal effects were observed for the combinations of GA-g-chitosans with β-lactams, and over 4.0 log CFU/mL reductions were observed after 24 h when combination treatment was used. These results may prove GA-g-chitosans to be a potent agent when combined with ampicillin and penicillin for the elimination of MRSA.

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Jin, Zheng, Kai Zhao, Gang Chen e Xu Zhang. "Preparation and Characterization of 2-Hydroxypropyltrimcthyl Ammonium Chloride Chitosan". Advanced Materials Research 183-185 (janeiro de 2011): 2216–20. http://dx.doi.org/10.4028/www.scientific.net/amr.183-185.2216.

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Chitosan has the potential to act as mediators of DNA transfection targeted to phagocytic cells such as macrophages, and to protect against biological degradation by nucleases as well as enhance gene expression. However, the poor solubility of Chitosan is the major limiting factor in its utilization. 2-hydroxypropyltrimcthyl ammonium chloride Chitosan has be prepared successfully through covalent binding of 2,3-Epoxypropyltrimethylammonium chloride ligands to the polymer’s primary amino groups and the polymer’s structure was verified with FT-IR spectra and NMR spectra. The new polymers were obtained with degree of quaternization (DQ) values around 34%, except in the case of the Phe-derived polymer, and thus possess reduced net positive charge as compared to the parent Chitosan. This study provided the new peptide-Chitosans with full water-solubility over practically the entire physiological pH range and led to more disordered. Globally, the new peptide Chitosans and especially the Asp-derived polymer, possess physico-chemical properties that turn them into promising candidates as novel Chitosan-based vaccine delivery systems.

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Rabea, E. I., e W. Steurbaut. "Chemically modified chitosans as antimicrobial agents against some plant pathogenic bacteria and fungi". Plant Protection Science 46, No. 4 (14 de dezembro de 2010): 149–58. http://dx.doi.org/10.17221/9/2009-pps.

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The antimicrobial activity of eight chemically modified chitosans against plant pathogenic bacteria of crown gall disease Agrobacterium tumefaciens and soft mould disease Erwinia carotovora and fungi of early blight disease Alternaria alternata, root rot disease Fusarium oxysporum, and damping off disease Pythium debaryanum was investigated. The minimum inhibitory concentration (MIC) of these compounds against the tested bacteria showed that N-(o,o-dichlorobenzyl)chitosan exhibited a high activity against A. tumefaciens and E. carotovora (MIC = 500 and 480 mg/l, respectively). In addition, the antifungal behaviour was investigated in vitro on mycelial growth and spore germination. N-(p-fluorobenzyl)chitosan was the most active against the mycelial growth of A. alternata with an EC50 of 703.4 mg/l, while the N-(o-chloro,o-fluorobenzyl)chitosan exhibited a high activity against F. oxysporum and P. debaryanum (EC50 = 641.2 and 155.7 mg/l, respectively). Against the fungal spore germination, all modified chitosans showed a higher inhibition of spore germination than unmodified chitosan. The compound of N-(o,o-di fluorobenzyl)chitosan exhibited a high inhibition percentage against A. alternata. However, N-(o-chlorobenzyl)chitosan and N-(p-chlorobenzyl)chitosan were significantly highly active against the spore germination of F. oxysporum.

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Vilcáez, Javier, e Tomohide Watanabe. "Inhibitory Effect of Gamma-Irradiated Chitosan on the Growth of Denitrifiers". International Journal of Microbiology 2009 (2009): 1–5. http://dx.doi.org/10.1155/2009/418595.

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In order to find an environmentally benign substitute to hazardous inhibitory agents, the inhibitory effect of -irradiated chitosans against a mixed culture of denitrifying bacteria was experimentally evaluated. Unlike other studies using pure aerobic cultures, the observed effect was not a complete inhibition but a transient inhibition reflected by prolonged lag phases and reduced growth rates. Raw chitosan under acid conditions (pH 6.3) exerted the strongest inhibition followed by the 100 kGy and 500 kGy irradiated chitosans, respectively. Therefore, because the molecular weight of chitosan decreases with the degree of -irradiation, the inhibitory properties of chitosan due to its high molecular weight were more relevant than the inhibitory properties gained due to the modification of the surface charge and/or chemical structure by -irradiation. High dosage of -irradiated appeared to increase the growth of mixed denitrifying bacteria in acid pH media. However, in neutral pH media, high dosage of -irradiation appeared to enhance the inhibitory effect of chitosan.

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de Oliveira, Ana Maria, Telma Teixeira Franco e Enio Nazaré de Oliveira Junior. "Physicochemical Characterization of Thermally Treated Chitosans and Chitosans Obtained by Alkaline Deacetylation". International Journal of Polymer Science 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/853572.

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The thermal depolymerization of chitosan and alkaline deacetylation of chitin were characterized by measurement of viscosity, gel permeation chromatography (GPC), potentiometric titration (PT), and proton nuclear magnetic resonance spectroscopy (H1NMR). The depolymerization rates (DR) measured by kinematic viscosity (KV), apparent viscosity (AV), and GPC (Mw) until 4 h of treatment wereDRKV=21.9,DRAV=25.5, andDRMw=23.3% h-1and for 5 to 10 h of treatment they decreased slowly to produce ofDRKV=0.545,DRAV=0.248, andDRMw=1.11% h-1. The mole fraction of N-acetylglucosamine residuesFAof chitosans was not modified after 10 h of thermal treatment at 100°C. The initialFAvalues of chitosan without any treatment wereFAPT=0.21andFAHNMR1=0.22and of chitosan treated for 10 h wereFAPT=0.27andFAHNMR1=0.22. The variables used to characterize the depolymerization process showed a good correlation. Six hours of thermal treatment as sufficient to obtain chitosans with a molar mass 90% smaller than that of the control chitosan without treatment.

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Linghu, Wen Sheng, e Chao Wang. "Adsorption of Heavy Metal Ions from Aqueous Solution by Chitosan". Advanced Materials Research 881-883 (janeiro de 2014): 570–73. http://dx.doi.org/10.4028/www.scientific.net/amr.881-883.570.

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In this work adsorption of heavy metal ions (Cu2+, Pb2+, Zn2+and Ni2+) from aqueous solution by chitosan was investigated in a batch reactor. Three commercially different viscosity chitosans were used as adsrobents. pH value, adsorption temperature, time and initial concentration had affected adsorption efficiency of metal ions. The results showed that low viscosity chitosan has the highest adsorption capacity among the low, middle and high viscosity chitosans. The amounts of adsorbed metal ions decreased with increased adsorption temperature and decreased pH value. The highest adsorbed amount at the equilibrium time (7.5mg/g) of Cu2+was observed among Cu2+, Pb2+, Zn2+and Ni2+.

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Chen, Zhi Qing, Quan Li Li, Quan Zen, Gang Li, Hao Bin Jiang, Laikui Liu e Brian W. Darvell. "Biomimetic Mineralization and Bioactivity of Phosphorylated Chitosan". Key Engineering Materials 288-289 (junho de 2005): 429–32. http://dx.doi.org/10.4028/www.scientific.net/kem.288-289.429.

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Phosphorylated chitosans were synthesized as templates to manipulate hydroxyapatite (HA) crystal nucleation, growth and microstructure. Two kinds of insoluble phosphorylated chitosan were soaked in saturated Ca(OH)2 solution for 4 d and in 1.5× SBF (simulated body fluid) solutions for 14 d at 37 °C for biomimetic mineralization. A lower [P]-content of phosphorylated chitosan promoted greater mineralization than higher [P]-content. Phosphorylated chitosan inhibited osteoblast proliferation and differentiation in vitro, while calcium phosphate phosphorylated chitosan composites did not.

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Razdan, A., e D. Pettersson. "Effect of chitin and chitosan on nutrient digestibility and plasma lipid concentrations in broiler chickens". British Journal of Nutrition 72, n.º 2 (agosto de 1994): 277–88. http://dx.doi.org/10.1079/bjn19940029.

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Broiler chickens were fed on a control diet based on maize and maize starch or diets containing chitin, or 94, 82 or 76% deacetylated chitin (chitosans) with different viscosities (360, 590 and 620 m Pa.s respectively) at an inclusion level of 30 g/kg. Animals had free access to feed and water for the whole experimental period. On days 10 and 18 of the experiment chickens given the control and chitin-containing diets weighed more, had consumed more feed and had lower feed conversion ratios (g feed/g weight gain) than chitosan-fed birds. Feeding of chitosan-containing diets generally reduced total plasma cholesterol and high-density-lipoprotein (HDL)-cholesterol concentrations and gave an increased HDL:total cholesterol ratio in comparison with chickens given the control and chitin-containing diets. However, no significant reductions in plasma triacylglycerol concentrations resulting from feeding of the chitosan-containing diets were observed. The reduction in total cholesterol concentration and increased HDL: total cholesterol ratio were probably caused by enhanced reverse cholesterol transport in response to intestinal losses of dietary fats. The suggestion that dietary fat absorption was impeded by the chitosans was strengthened by the observation that ileal fat digestibility was reduced by 26% in comparison with control and chitin-fed animals. In a plasma triacylglycerol response study on day 21, feeding of 94 and 76%-chitosan-containing diets generally reduced postprandial triacylglycerol concentrations compared with chickens given the chitin-containing diet. Duodenal digestibilities of nutrients amongst chickens given the chitin-containing diet were generally lower than those of control and chitosan-fed birds indicating decreased intestinal transit time. The reduced caecal short-chain fatty acid concentrations of chickens given chitosan diets compared with the control diet illustrates the antimicrobial nature of chitosan. The fact that the three chitosan-containing diets affected the registered variables similarly indicated that the level of inclusion of chitosans in the diet exceeded the level at which the effect of the different viscosities could be significant.

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Benabbou, R., A. Zihler, M. Desbiens, E. Kheadr, M. Subirade e I. Fliss. "Inhibition ofListeria monocytogenesby a combination of chitosan and divergicin M35". Canadian Journal of Microbiology 55, n.º 4 (abril de 2009): 347–55. http://dx.doi.org/10.1139/w08-154.

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The antimicrobial activities of the class IIa bacteriocin divergicin M35 and several types of chitosan against Listeria monocytogenes were quantified by agar diffusion, critical micro-dilution, and viable count and observed by electron microscopy. Antimicrobial activity of chitosan depended on its molecular mass (MM) and the pH. Three chitosans with MM values of 2, 20, and 100 kDa and 87.4% degree of deacetylation (DDA) were chosen for further study, based on high anti-listerial activity at pH 4.5. Electron microscopy suggested that the mechanism of anti-listerial activity also varied with the MM. Low-MM chitosan appeared to inhibit L. monocytogenes by affecting cell permeability and growth, whereas medium- and high-MM chitosan may form a barrier on the cell surface that prevents entry of nutrients. The minimum inhibitory concentrations (MICs) of 2, 20, and 100 kDa chitosan and divergicin M35 against a divergicin-resistant strain of L. monocytogenes (LSD 535) were 2.5, 2.5, 0.625, and 0.25 mg/mL, respectively. The combination of any of these 3 chitosans and divergicin M35 appeared to have an additive effect against L. monocytogenes, as determined by fractional inhibitory concentration (FIC) index. This study provides useful data for the development of chitosan films incorporating divergicin M35 for inhibiting L. monocytogenes in foods.

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MOOLPHUERK, Namphueng, e Wattana PATTANAGUL. "Pretreatment with different molecular weight chitosans encourages drought tolerance in rice (Oryza sativa L.) seedling". Notulae Botanicae Horti Agrobotanici Cluj-Napoca 48, n.º 4 (22 de dezembro de 2020): 2072–84. http://dx.doi.org/10.15835/nbha48412018.

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Drought is a critical environmental constraint limiting plant growth and productivity. Chitosan has been utilized as a potential biostimulant and proven to be effective against drought stress in many plant species. The objective of this study was to determine the effects of pretreatment with different molecular weight (MW) chitosans on some physiological characteristics of rice seedlings under drought stress. Rice seedlings were treated with low (50-190 kDa), medium (190-310 kDa) and high (310-375 kDa) MW chitosans by seed priming and foliar spray. The seedlings were subjected to drought by withholding water for four days. The relative water content (RWC) was reduced from 93% in the control plants to 74% in the droughted plants. The results revealed that treating with chitosan, especially with low MW chitosan, promoted root growth under drought stress. All chitosan treatments led to higher relative water content and photosynthetic pigment under drought condition. Pretreatment with chitosan also induced sugar accumulation, and treating with low MW chitosan significantly increased starch accumulation under drought stress. In addition, chitosan treatments alleviated the effects caused by drought stress as represented by the decreases in electrolyte leakage, malondialdehyde (MDA) as well as hydrogen peroxide (H2O2), corresponding with the increases in activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX) activity.

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Sánchez, Luis-Felipe, Jimmy Cánepa, Suyeon Kim e Javier Nakamatsu. "A Simple Approach to Produce Tailor-Made Chitosans with Specific Degrees of Acetylation and Molecular Weights". Polymers 13, n.º 15 (22 de julho de 2021): 2415. http://dx.doi.org/10.3390/polym13152415.

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Chitin is a structural polysaccharide that is found in crustaceans, insects, fungi and some yeasts. Chitin deacetylation produces chitosan, a well-studied biopolymer with reported chemical and biological properties for diverse potential applications for drug delivery, metal ion absorption, scaffolds and tissue engineering. Most known properties of chitosan have been determined from samples obtained from a variety of sources and in different conditions, this is, from chitosans with a wide range of degrees of N-acetylation (DA) and molecular weight (MW). However, as for any copolymer, the physicochemical and mechanical characteristics of chitosan highly depend on their monomer composition (DA) and chain size (MW). This work presents a simple methodology to produce chitosans with specific and predictive DA and MW. Reaction with acetic anhydride proved to be an efficient method to control the acetylation of chitosan, DAs between 10.6% and 50.6% were reproducibly obtained. In addition to this, MWs of chitosan chains were reduced in a controlled manner in two ways, by ultrasound and by acidic hydrolysis at different temperatures, samples with MWs between 130 kDa and 1300 kDa were obtained. DAs were determined by 1H-NMR and MWs by gel permeation chromatography.

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Okhota, E. V., A. I. Chepkasova, E. P. Karaulova e T. N. Slutskaya. "SUBSTANTIATION OF POSSIBILITY TO USE WASTE OF SEA CUCUMBER PROCESSING FOR PRODUCTION OF SOFT DRINKS". Izvestiya TINRO 200 (26 de março de 2020): 221–28. http://dx.doi.org/10.26428/1606-9919-2020-200-221-228.

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The broth of sea cucumber was decolorized with mineral sorbents, as perlite and bentonite, and with chitosans of crab carapace and shrimp shell. The chitosans were the most effective in sorption and subsequent removal of the protein-pigment complex, providing the decolorization degree of 35–55 %. Besides, the content of glycosides in the broth was twice decreased. The amino sugars content changed in dependence on the chitosan origin: the chitosan of crab carapace did not influence on this parameter, but the chitosan of shrimp shell caused its halving. For the optimal combination of chemical compounds in the broth, the chitosan with high molecular weight (1300 kDa) extracted from crab carapace should be used for decolorizing. Preliminary fermentation of the broth with Protamex increased concentration of biologically active peptides with low molecular weight in the solution. The fermented and decolorized broth of sea cucumber has good organoleptic properties and high content of biologically active components, as glycosides, amino sugars and low molecular weight peptides, so could be used as the basis for nonalcoholic tonic drinks.

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Huang, Jun, Jian Wei Mao, Sheng Hu, Dong Ke Zhao, Le He Mei, Shi Wang Liu, Yuan Feng Wu, Sheng Fang e Qian Shao. "Ultrasonic-Assisted Preparation, Characterization and Antibacterial Activity of β-Chitosan from Squid Pens". Advanced Materials Research 236-238 (maio de 2011): 282–87. http://dx.doi.org/10.4028/www.scientific.net/amr.236-238.282.

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β-chitosan preparation from squid pens was carried out using aqueous NaOH with the ultrasonic assistance. Single factor experiments and L9(34) orthogonal experiments were used to investigate the effect of three parameters (reaction time, concentration of NaOH and reaction temperature) on deacetylation of β-chitin. The optimal conditions for deacetylation of chitin were reaction temperature 80°C, reaction time 2 h and concentration of NaOH 50%. The optimal conditions allowed deacetylation degree of β-chitin from 71.32% to 92.91%. The β-chitosan from squid pens was confirmed by Fourier transform infrared spectroscopy. The antibacterial activities of the prepared β-chitosans againstaphylococcus aureus(S. aureus) andEscherchia coli(E.coli) were then determined and compared by the MIC (minimum inhibitory concentration). Results indicate that β-chitosans with different degrees of deacetylation (DD) possess different antibacterial activity. The growth ofS. aureuscan be easily inhibited by prepared β-chitosan thanE.coli.

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Huang, Li Xin. "Anti-Bacterial and Crease-Resist Finishing of Cotton Fabrics with Chrysalis Chitosan". Advanced Materials Research 287-290 (julho de 2011): 2693–96. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.2693.

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Cotton fabrics is treated for bacterial repellency and crease resistance with different kinds of chitosans. Through the study and test of the main processing parameters of chrysalis chitosan, the optimized finishing parameters are obtained. Then the anti-bacterial and crease-resist mechanism of chitosan as well as the washing resistance of finished fabrics is measured and analyzed.

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Tirado-Gallegos, Juan Manuel, Paul Baruk Zamudio-Flores, Miguel Espino-Díaz, René Salgado-Delgado, Gilber Vela-Gutiérrez, Francisco Hernández-Centeno, Haydee Yajaira López-De la Peña, María Hernández-González, J. Rodolfo Rendón-Villalobos e Adalberto Ortega-Ortega. "Chitosan Films Obtained from Brachystola magna (Girard) and Its Evaluation on Quality Attributes in Sausages during Storage". Molecules 26, n.º 6 (22 de março de 2021): 1782. http://dx.doi.org/10.3390/molecules26061782.

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High molecular weight chitosan (≈322 kDa) was obtained from chitin isolated from Brachystola magna (Girard) to produced biodegradable films. Their physicochemical, mechanical and water vapor permeability (WVP) properties were compared against commercial chitosan films with different molecular weights. Brachystola magna chitosan films (CFBM) exhibited similar physicochemical and mechanical characteristics to those of commercial chitosans. The CFBM films presented lower WVP values (10.01 × 10−11 g/m s Pa) than commercial chitosans films (from 16.06 × 10−11 to 64.30 × 10−11 g/m s Pa). Frankfurt-type sausages were covered with chitosan films and stored in refrigerated conditions (4 °C). Their quality attributes (color, weight loss, pH, moisture, texture and lipid oxidation) were evaluated at 0, 5, 10, 15 and 20 days. Sausages covered with CFMB films presented the lowest weight loss (from 1.24% to 2.38%). A higher increase in hardness (from 22.32 N to 30.63 N) was observed in sausages covered with CFMB films. Compared with other films and the control (uncovered sausages), CFMB films delay pH reduction. Moreover, this film presents the lower lipid oxidation level (0.10 malonaldehyde mg/sample kg). Thus, chitosan of B. magna could be a good alternative as packaging material for meat products with high-fat content.

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Kuenne, Sven, e Frederik Püttmann. "Influence of Acetylation and Polymerization Degree of Chitosan As Green Binder Material for LiMn₂O₄ Positive Electrodes in Lithium Ion Batteries". ECS Meeting Abstracts MA2022-01, n.º 2 (7 de julho de 2022): 238. http://dx.doi.org/10.1149/ma2022-012238mtgabs.

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The increasing market of lithium ion batteries within the climate crisis consequently leads to a need of environmentally friendly battery materials and production. Organic solvents, fluorinated binders and toxic transition metals are common components in state-of-the-art batteries. Aqueously processed ecofriendly electrodes are reported showing high electrical performance combined with high work safety and sustainability. In this study, the biopolymer chitosan is investigated electrochemically and mechanically as green binder for positive electrodes utilizing lithium manganese oxide (LiMn2O4; LMO) for the first time. Therefore, chitosans were tailored to a high and low degree of polymerization (DP) and three comparable degrees of acetylation (DA). The systematical comparison of these binder materials reveals insights into the impact of polymer binder properties on the electrochemical performance of positive electrodes. Low DP chitosan show a higher adhesive strength than high DP chitosans or PVdF, while chitosan-based electrodes with DA<16% deliver higher discharge capacities and Coulombic efficiencies in T-type cells than with DA>16% or even with the state-of-the-art binder polyvinylidene difluoride (PVdF). Crosslinking of chitosans with citric acid (CA) further increases discharge capacities up to 80 mAh g-1 at 10C and shows again a superior electrochemical performance with sustainable battery materials. Figure 1

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Raafat, Dina, Kristine von Bargen, Albert Haas e Hans-Georg Sahl. "Insights into the Mode of Action of Chitosan as an Antibacterial Compound". Applied and Environmental Microbiology 74, n.º 12 (2 de maio de 2008): 3764–73. http://dx.doi.org/10.1128/aem.00453-08.

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ABSTRACT Chitosan is a polysaccharide biopolymer that combines a unique set of versatile physicochemical and biological characteristics which allow for a wide range of applications. Although its antimicrobial activity is well documented, its mode of action has hitherto remained only vaguely defined. In this work we investigated the antimicrobial mode of action of chitosan using a combination of approaches, including in vitro assays, killing kinetics, cellular leakage measurements, membrane potential estimations, and electron microscopy, in addition to transcriptional response analysis. Chitosan, whose antimicrobial activity was influenced by several factors, exhibited a dose-dependent growth-inhibitory effect. A simultaneous permeabilization of the cell membrane to small cellular components, coupled to a significant membrane depolarization, was detected. A concomitant interference with cell wall biosynthesis was not observed. Chitosan treatment of Staphylococcus simulans 22 cells did not give rise to cell wall lysis; the cell membrane also remained intact. Analysis of transcriptional response data revealed that chitosan treatment leads to multiple changes in the expression profiles of Staphylococcus aureus SG511 genes involved in the regulation of stress and autolysis, as well as genes associated with energy metabolism. Finally, a possible mechanism for chitosan's activity is postulated. Although we contend that there might not be a single classical target that would explain chitosan's antimicrobial action, we speculate that binding of chitosan to teichoic acids, coupled with a potential extraction of membrane lipids (predominantly lipoteichoic acid) results in a sequence of events, ultimately leading to bacterial death.

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Gubaeva, Ekaterina, Airat Gubaev, Rebecca L. J. Melcher, Stefan Cord-Landwehr, Ratna Singh, Nour Eddine El Gueddari e Bruno M. Moerschbacher. "‘Slipped Sandwich’ Model for Chitin and Chitosan Perception in Arabidopsis". Molecular Plant-Microbe Interactions® 31, n.º 11 (novembro de 2018): 1145–53. http://dx.doi.org/10.1094/mpmi-04-18-0098-r.

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Chitin, a linear polymer of N-acetyl-d-glucosamine, and chitosans, fully or partially deacetylated derivatives of chitin, are known to elicit defense reactions in higher plants. We compared the ability of chitin and chitosan oligomers and polymers (chitin oligomers with degree of polymerization [DP] 3 to 8; chitosan oligomers with degree of acetylation [DA] 0 to 35% and DP 3 to 15; chitosan polymers with DA 1 to 60% and DP approximately 1,300) to elicit an oxidative burst indicative of induced defense reactions in Arabidopsis thaliana seedlings. Fully deacetylated chitosans were not able to trigger a response; elicitor activity increased with increasing DA of chitosan polymers. Partially acetylated chitosan oligomers required a minimum DP of 6 and at least four N-acetyl groups to trigger a response. Invariably, elicitation of an oxidative burst required the presence of the chitin receptor AtCERK1. Our results as well as previously published studies on chitin and chitosan perception in plants are best explained by a new general model of LysM-containing receptor complexes in which two partners form a long but off-set chitin-binding groove and are, thus, dimerized by one chitin or chitosan molecule, sharing a central GlcNAc unit with which both LysM domains interact. To verify this model and to distinguish it from earlier models, we assayed elicitor and inhibitor activities of selected partially acetylated chitosan oligomers with fully defined structures. In contrast to the initial ‘continuous groove’, the original ‘sandwich’, or the current ‘sliding mode’ models for the chitin/chitosan receptor, the here-proposed ‘slipped sandwich’ model—which builds on these earlier models and represents a consensus combination of these—is in agreement with all experimental observations.

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Mezzetta, Andrea, Lorenzo Guazzelli e Cinzia Chiappe. "Access to cross-linked chitosans by exploiting CO2 and the double solvent-catalytic effect of ionic liquids". Green Chemistry 19, n.º 5 (2017): 1235–39. http://dx.doi.org/10.1039/c6gc02935c.

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CHEN, CHEE-SHAN, WAN-YU LIAU e GUO-JANE TSAI. "Antibacterial Effects of N-Sulfonated and N-Sulfobenzoyl Chitosan and Application to Oyster Preservation". Journal of Food Protection 61, n.º 9 (1 de setembro de 1998): 1124–28. http://dx.doi.org/10.4315/0362-028x-61.9.1124.

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The antibacterial effects of sulfonated and sulfobenzoyl chitosans were evaluated and compared with that of 69% deacetylated chitosan (DD69 chitosan). Minimal inhibitory concentrations of sulfonated chitosan (SC1, 0.63% sulfur content) against Shigella dysenteriae, Aeromonas hydrophila, Salmonella typhimurium, and Bacillus cereus were found to be lower than those of DD69 chitosan. A high sulfur content in sulfonated chitosan adversely influenced its antibacterial effect. Sulfobenzoyl chitosan (SBC) has excellent water solubility and an antibacterial effect comparable to that of SC1. SBC at 1,000 and 2,000 ppm extended the shelf life of oysters at 5°C by 4 days at the former or by 7 days at least at the latter concentration. The growth of coliforms and Pseudomonas, Aeromonas, and Vibrio species on oysters was retarded by the addition of DD69 chitosan or SBC.

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TSAI, GUO-JANE, e WEN-HUEY SU. "Antibacterial Activity of Shrimp Chitosan against Escherichia coli". Journal of Food Protection 62, n.º 3 (1 de março de 1999): 239–43. http://dx.doi.org/10.4315/0362-028x-62.3.239.

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The effects of cell age, reaction temperature, pH value, and salts on the inhibitory activity of shrimp chitosan (98% deacetylated) against Escherichia coli were investigated. The age of a bacterial culture affected its susceptibility to chitosan, with cells in the late exponential phase being most sensitive to chitosan. Higher temperature (25 and 37°C) and acidic pH increased the bactericidal effects of chitosan. Sodium ions (100 mM Na+) might complex with chitosan and accordingly reduce chitosan's activity against E. coli. Divalent cations at concentrations of 10 and 25 mM reduced the antibacterial activity of chitosan, in the order of Ba2+ > Ca2+ > Mg2+. Chitosan also caused leakage of glucose and lactate dehydrogenase from E. coli cells. These data support the hypothesis that the mechanism of chitosan antibacterial action involves a cross-linkage between the polycations of chitosan and the anions on the bacterial surface that changes the membrane permeability.

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Liu, Qili, Jianxin Zhang, Dong Li, Jianfeng Lang, Shasha Zai, Jianjun Hao e Xiaohui Wang. "Inhibition of Amphiphilic N-Alkyl-O-carboxymethyl Chitosan Derivatives on Alternaria macrospora". BioMed Research International 2018 (11 de junho de 2018): 1–9. http://dx.doi.org/10.1155/2018/5236324.

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Cotton leaf spot (Alternaria macrospora) is a widespread disease that occurs in the main cotton-producing area of China. In managing this disease, a novel chitosan-based biopesticide, an amphiphilic N-alkyl-O-carboxymethyl chitosan derivative, was prepared. The product was selected from variations of chitosan with different molecular structures, which were obtained via a two-step reaction. First, carboxymethyl chitosans with varying molecular sizes were obtained by etherification with chloroacetic acid; then the carboxymethyl chitosan was alkylated with C4–C12 fatty aldehyde through a Schiff-base reaction. This procedure resulted in derivatives of amphiphilic N-alkyl-O-carboxymethyl chitosan, which showed strong antifungal activities against A. macrospora, and the efficacy was determined by its molecular structure.

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Junaidi, Ahmad Budi, Indriana Kartini e Bambang Rusdiarso. "CHITOSAN PREPARATION WITH MULTISTAGE DEACETYLATION OF CHITIN AND INVESTIGATION OF ITS PHYSICOCHEMICAL PROPERTIES". Indonesian Journal of Chemistry 9, n.º 3 (24 de junho de 2010): 369–72. http://dx.doi.org/10.22146/ijc.21500.

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Study of chitosan prepared with chitin deacetylation by multistage alkali treatments has been done. Chitin was extracted from Lampung white shrimp's (Litophenaeus vannamei) shell. The FTIR spectroscopy was used to determine deacetylation degree of chitin/chitosan. Viscometry was used to determine molecular weight of chitosan. Effect of chitin deacetylation by multistage alkali treatments toward deacetylation degree and molecular weight was studied by comparingit with continuous alkali treatment. The results showed that chitosan prepared by multistage alkali treatment had higher deacetylation degree than those of obtained by continuous alkali treatment. Multistage alkali treatment does not influence the chitosan's molecular weight. Despite its significant effect on the deacetylation process, concentration of alkali does not significantly effect the process of depolimerization. Keywords: chitin, chitosan, multistage treatments, deacetylation degree, molecular weight

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Badawy, M. E. I., e A. F. El-Aswad. "Insecticidal activity of chitosans of different molecular weights and chitosan-metal complexes against cotton leafworm Spodoptera littoralis and oleander aphid Aphis nerii". Plant Protection Science 48, No. 3 (27 de julho de 2012): 131–41. http://dx.doi.org/10.17221/67/2010-pps.

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As an alternative to synthetic pesticides, chitosan has received much attention as a biopolymer active against some agricultural pests. The, insecticidal activity of chitosans of four molecular weights (2.27 × 105,3.60 × 105,5.97 × 105,and9.47 × 105 g/mol) was investigated against two species of arthropod pests: oleander aphid Aphis nerii and cotton leafworm Spodoptera littoralis. In addition, the most active chitosan of 2.27 × 105 g/mol was chemically modified with metals of Ag(I), Cu(II), Ni(II), and Hg(II) to give corresponding chitosan-metal complexes. Larval mortality, growth inhibition, and antifeedant activities for third instar larvae of S. littoralis were evaluated at 4 g (a.i.) chitosan/kg diet. Chitosan of 2.27 × 105 g/mol and its complexes with Ni and Hg were the most active compounds. The results against A. nerii indicated that chitosans of 3.60 × 105 and 5.97 × 105 g/mol showed high activity among the different molecular weights in leaf-dip bioassay after 24 h of treatment with 48 and 49% mortalities, respectively, at 1000 mg/l. All compounds had a systemic effect against A. nerii. Chitosans of 2.27 × 105,3.60 × 105,and5.97 × 105 g/mol showed the highest efficacy at all concentrations tested; however, chitosan-Cu was significantly the most active among the complexes.

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Mathaba, Machodi, e Michael Olawale Daramola. "Effect of Chitosan’s Degree of Deacetylation on the Performance of PES Membrane Infused with Chitosan during AMD Treatment". Membranes 10, n.º 3 (24 de março de 2020): 52. http://dx.doi.org/10.3390/membranes10030052.

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Acid mine drainage is an environmental problem associated with mining operations and activities. Its treatment is essential to achieving environmental sustainability. In this study, a polyethersulphone (PES) membrane infused with chitosan is proposed as a point-of-use material for treating acid mine drainage (AMD). The composite material explored the synergetic effect between chitosan and polymer, particularly considering the effect of the degree of deacetylation (DD) of chitosan on the performance of membrane. Chitosan was produced from chitin under various synthesis process conditions and infused within polyethersulphone membrane. The results obtained show that chitosan with the highest degree of deacetylation was achieved with a temperature of 100 °C and NaOH concentration of 40 wt%. Increasing the temperature above 100 °C started degrading already formed or exposed amine groups, thus, reducing the DD of the chitosan sample. The contact angle and porosity analysis indicated that the hydrophilic nature of the membrane was enhanced with increasing DD of the chitosan. The performance of the membranes was conducted on a Dead-end filtration cell using synthetic acid mine drainage. The results showed that the flux and rejection of the membrane was enhanced with increasing degree of deacetylation. PES 5 and PES 1 were blended with chitosan having the highest (95.97%) and lowest (33.93%) degree of deacetylation, respectively. PES 5 reported pure water flux of 123 L/m2·h and PES 1 was recorded as 104 L/m2·h. Similarly, the rejection of the membrane was improved with increasing chitosan’s degree of deacetylation. PES 5 had higher rejection and PES 1 had the least rejection. Maximum rejection for the contaminants was determined as 98.05, 97.39, 96.25, 95.24 and 80.34% for Mn2+, Fe2+, Mg2+ and Ca2+ and SO42−, respectively. The results obtained show that chitosan’s degree of deacetylation has a positive effect on the performance of polyethersulphone membrane during the treatment of acid mine drainage.

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Kim, Hee Kyong, Hye Ji Noh, Hyang Hyun Cho e Hong Bum Koh. "Development of Chitosan Based Natural Antibiotics for Diarrheal Treatment III. Evaluation for the Effects of Persistant Treatments of Chitosan Oligosaccharide on the Formation of Tolerance against E.coli". Journal of Chitin and Chitosan 21, n.º 2 (30 de junho de 2016): 109–17. http://dx.doi.org/10.17642/jcc.21.2.6.

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Sivanesan, Iyyakkannu, Judy Gopal, Manikandan Muthu, Juhyun Shin e Jae-Wook Oh. "Reviewing Chitin/Chitosan Nanofibers and Associated Nanocomposites and Their Attained Medical Milestones". Polymers 13, n.º 14 (16 de julho de 2021): 2330. http://dx.doi.org/10.3390/polym13142330.

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Chitin/chitosan research is an expanding field with wide scope within polymer research. This topic is highly inviting as chitin/chitosan’s are natural biopolymers that can be recovered from food waste and hold high potentials for medical applications. This review gives a brief overview of the chitin/chitosan based nanomaterials, their preparation methods and their biomedical applications. Chitin nanofibers and Chitosan nanofibers have been reviewed, their fabrication methods presented and their biomedical applications summarized. The chitin/chitosan based nanocomposites have also been discussed. Chitin and chitosan nanofibers and their binary and ternary composites are represented by scattered superficial reports. Delving deep into synergistic approaches, bringing up novel chitin/chitosan nanocomposites, could help diligently deliver medical expectations. This review highlights such lacunae and further lapses in chitin related inputs towards medical applications. The grey areas and future outlook for aligning chitin/chitosan nanofiber research are outlined as research directions for the future.

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