Topic
Chitin
About: Chitin is a research topic. Over the lifetime, 6590 publications have been published within this topic receiving 253993 citations.
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01 Jan 1994TL;DR: The molecular weight dependency of antimicrobial activity by various chitosan oligomers was mainly investigated together with regulation of Mw distribution and chemical analysis of the degree of N-deacetylation.
Abstract: Chitin, a natural abundant mucopolysaccharide becomes to draw many attentions as a multifunctional polymer owing to the variety of biological activities in spite of its poor solubility. Chitosan, N-deacetylated form of chitin, is also natural mucopolysaccharide as a supporting polymer of fungi or yeast. The chemical structure of chitosan is β-1,4 linked linear polymer of 2- acetoamide-2-deoxy-β-D-glucose and 2-amino-2-deoxy-β-D-glucose, respectively as shown in Scheme. As seen in Scheme, chemical structures of cellulose and chitosan are very close expect C- 2 position of glucose units. Chitosan becomes amorphous with the progress of N-deacetylation and to more susceptible for chitosanase produced by a limited number of microbials. Although chitosan itself is water insoluble and be solubilized by the formation of salt with organic acids such as formic acid, acetic acid and etc., chitosan oligomers become water soluble even without organic acid. Chitosan and chitosan oligomers are reported to show several biological activities such as anticancer activity1, antifungal activity2 and phytoalexin elicitor activity for a plant3. The toxicity of chitosan was investigated through oral dose for 19 days by 18 g/Kg of mouse body weight days and confirmed to be low immunogenicity together with low acute, semi-acute toxicities and faint mutational activity, although mouse intraperitoneal injection of chitosan-acetate salt induced peritoneal macrophage activation and immunoadjuvant activity. As mentioned before, chitosan and its hydrolysates are reported to show a specific antibacterial and antifungal activities, in which a slightly hydrolyzed chitosan showed the highest antimicrobial activity followed by chitosan of high molecular weight4. The minimum growth inhibitions were shown by chitosan oligomers of less than 6 glucosamine residues. However, the mechanism for the antimicrobial activity is not clear enough, because regulation of molecular weight (Mw) distribution has not been achieved on chitosan hydrolysates yet. In the present study, the molecular weight dependency of antimicrobial activity by various chitosan oligomers was mainly investigated together with regulation of Mw distribution and chemical analysis of the degree of N-deacetylation.
92 citations
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TL;DR: In this paper, a new protocol for the first derivative UV method using concentrated phosphoric acid as a solvent for highly acetylated chitin was developed in order to determine degree of acetylation.
92 citations
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TL;DR: A soil bacterium, Bacillus sp.
Abstract: A soil bacterium, Bacillus sp. strain BC121, isolated from the rhizosphere of sorghum, showed high antagonistic activity against Curvularia lunata. A clear inhibition zone of 0.5-1 cm was observed in dual plate assay. After 10 days of incubation, the bacterial strain grew over the fungal mycelial surface and multiplied extensively on it. Scanning electron microscopic observations showed a clear hyphal lysis and degradation of fungal cell wall. In dual cultures, the Bacillus strain BC121 inhibited the C. lunata up to 60% in terms of dry weight. This strain also produced a clear halo region on chitin agar medium plates containing 0.5% colloidal chitin, indicating that it excretes chitinase. The role of the Bacillus strain BC121 in suppressing the fungal growth in vitro was studied in comparison with a mutant of that strain, which lacks both antagonistic activity and chitinolytic activity. The extra-cellular protein precipitate from Bacillus strain BC121 culture filtrate had significant growth-retarding effect and mycolytic activity on C. lunata. The protein extract from the wild strain, when tested on SDS-PAGE gel showed a unique band corresponding to the molecular mass of 25 kDa, which could be the probable chitinase protein.
92 citations
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TL;DR: An exceptionally stable extracellular chitinase is induced in Aspergillus fumigatus YJ-407 by using ammonium sulfate precipitation followed by DEAE-cellulose chromatography and preparative PAGE and analysis of the hydrolysis product showed that the enzyme has both endo- and exo-hydrolytic activities.
Abstract: Chitinases are produced throughout the growth process of fungi and are thought to play important roles in morphogenesis. Aspergillus fumigatus, is an important pathogen of immunocompromised individuals in which it causes pneumonia and invasive disseminated disease with high mortality; it is also known to produce chitinase. We have induced an exceptionally stable extracellular chitinase in A. fumigatus YJ-407, which could be isolated readily in a homogeneous form by using ammonium sulfate precipitation followed by DEAE-cellulose chromatography and preparative PAGE. The molecular mass of this chitinase was estimated to be 46 000 by SDS/PAGE, and its isoelectric point was pH 5.6. The enzyme was most active at pH 5.0 and 60 degrees C, and was inhibited strongly by Hg2+, Pb2+, Ag+, Fe2+, Mn2+ and Zn2+. The enzyme was stable over a broad pH range 4-8 and below 45 degrees C. Tryptophan and carboxyl groups were found to be essential for the enzyme activity. The Michaelis constants for swollen chitin and chitosan were 1.12 mg.mL-1 and 1.84 mg.mL-1, respectively. The enzyme showed maximum activity towards glycol chitin and partially deacetylated chitosan, and lower activity towards colloidal chitin. Analysis of the hydrolysis product showed that the enzyme has both endo- and exo-hydrolytic activities. In addition, a transglycosyl activity was also observed.
92 citations
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TL;DR: Chitin structure isolated from both sexes of four grasshopper species showed that the chitin was in the alpha form, with respect to gender, and the elemental analysis, thermal properties, and crystalline index values were similar in males and females.
Abstract: In this study, we used Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), thermogravimetric analysis (TGA), X-ray diffractometry (XRD), and scanning electron microscopy (SEM) to investigate chitin structure isolated from both sexes of four grasshopper species. FT-IR, EA, XRD, and TGA showed that the chitin was in the alpha form. With respect to gender, two main differences were observed. First, we observed that the quantity of chitin was greater in males than in females and the dry weight of chitin between species ranged from 4.71% to 11.84%. Second, using SEM, we observed that the male chitin surface structure contained 25-90 nm wide nanofibers and 90-250 nm nanopores, while no pores or nanofibers were observed in the chitin surface structure of the majority of females (nanofibers were observed only in M. desertus females). In contrast, the elemental analysis, thermal properties, and crystalline index values for chitin were similar in males and females. Also, we carried out enzymatic digestion of the isolated chitins using commercial chitinase from Streptomyces griseus. We observed that there were no big differences in digestion rate of the chitins from both sexes and commercial chitin. The digestion rates were for grasshoppers' chitins; 88.45-95.48% and for commercial chitin; 94.95%.
92 citations