Chitin

About: Chitin is a research topic. Over the lifetime, 6590 publications have been published within this topic receiving 253993 citations.

Preparation and Characterization of Chitosan Obtained from Shells of Shrimp (Litopenaeus vannamei Boone)

Abstract: The main source of commercial chitosan is the extensive deacetylation of its parent polymer chitin It is present in green algae, the cell walls or fungi and in the exoskeleton of crustaceans A novel procedure for preparing chitosan from shrimp shells was developed The procedure involves two 10-minutes bleaching steps with ethanol after the usual demineralization and deproteinization processes Before deacetylation, chitin was immersed in 125 M NaOH, cooled down and kept frozen for 24 h The obtained chitosan was characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV, X-ray diffraction (XRD) and viscosimetry Samples of white chitosan with acetylation degrees below 9 % were obtained, as determined by FTIR and UV-first derivative spectroscopy The change in the morphology of samples was followed by SEM The ash content of chitosan samples were all below 0063 % Chitosan was soluble in 1 % acetic acid with insoluble contents of 062 % or less XRD patterns exhibited the characteristic peaks of chitosan centered at 10 and 20 degrees in 2 θ The molecular weight of chitosan was between 23 and 28 × 10 5 g/mol It is concluded that the procedure developed in the present work allowed obtaining chitosans with physical and chemical properties suitable for pharmaceutical applications

Physicochemical properties and bioactivity of fungal chitin and chitosan.

Abstract: Chitinous material was extracted from mycelia of Aspergillus niger and Mucor rouxii grown in yeast peptone dextrose broth for 15 and 21 days, respectively. The extracted material was characterized for purity, degree of acetylation, and crystallinity and tested for antibacterial and eliciting properties. The maximum glucosamine level determined in the mycelium of A. niger was 11.10% dw and in the mycelium of M. rouxii was 20.13% dw. On the basis of the stepwise extraction of freeze-dried mycelia, it appeared that M. rouxii mycelia contained both chitin and chitosan, whereas A. niger contained only chitin. The yields of crude chitin from A. niger and M. rouxii were 24.01 and 13.25%, respectively, and the yield of chitosan from M. rouxii was 12.49%. Significant amounts (7.42-39.81%) of glucan were associated with chitinous compounds from both species and could not be eliminated by the extraction method used. The degrees of acetylation were determined to be 76.53 and 50.07% for chitin from A. niger and M. rouxii, respectively, and 19.5% for M. rouxii chitosan. The crystallinity of fungal chitin and chitosan was estimated to be less intense than in corresponding materials from shrimp shells. The extracted chitin and chitosan in a concentration of 0.1% reduced Salmonella Typhimurium DT104 2576 counts by 0.5-1.5 logs during a 4 day incubation in tryptic soy broth at 25 °C. Furthermore, all tested chitinous materials from fungal sources significantly reduced lesions caused by Botrytis cinerea and Penicillium expansum in harvested apples.

Increase in chitin as an essential response to defects in assembly of cell wall polymers in the ggp1delta mutant of Saccharomyces cerevisiae.

Abstract: The GGP1/GAS1 gene codes for a glycosylphosphatidylinositol-anchored plasma membrane glycoprotein of Saccharomyces cerevisiae. The ggp1delta mutant shows morphogenetic defects which suggest changes in the cell wall matrix. In this work, we have investigated cell wall glucan levels and the increase of chitin in ggp1delta mutant cells. In these cells, the level of alkali-insoluble 1,6-beta-D-glucan was found to be 50% of that of wild-type cells and was responsible for the observed decrease in the total alkali-insoluble glucan. Moreover, the ratio of alkali-soluble to alkali-insoluble glucan almost doubled, suggesting a change in glucan solubility. The increase of chitin in ggp1delta cells was found to be essential since the chs3delta ggp1delta mutations determined a severe reduction in the growth rate and in cell viability. Electron microscopy analysis showed the loss of the typical structure of yeast cell walls. Furthermore, in the chs3delta ggp1delta cells, the level of alkali-insoluble glucan was 57% of that of wild-type cells and the alkali-soluble/alkali-insoluble glucan ratio was doubled. We tested the effect of inhibition of chitin synthesis also by a different approach. The ggp1delta cells were treated with nikkomycin Z, a well-known inhibitor of chitin synthesis, and showed a hypersensitivity to this drug. In addition, studies of genetic interactions with genes related to the construction of the cell wall indicate a synthetic lethal effect of the ggp1delta kre6delta and the ggp1delta pkc1delta combined mutations. Our data point to an involvement of the GGP1 gene product in the cross-links between cell wall glucans (1,3-beta-D-glucans with 1,6-beta-D-glucans and with chitin). Chitin is essential to compensate for the defects due to the lack of Ggp1p. Moreover, the activities of Ggp1p and Chs3p are essential to the formation of the organized structure of the cell wall in vegetative cells.

Applications of biopolymers I: chitosan

Abstract: Chitosan is prepared from chitin, the second most abundant natural polymer in the world. It is primarily composed of glucosamine and N-acetyl glucosamine residues with a 1,4-β-linkage. It can be obtained by deacetylation of chitin, which is produced from shells of crustaceans, insects, and other sources. Chitosan is a nontoxic, biodegradable, and biocompatible natural polymer and can be used in a wide range of applications such as in the areas of biomedicine, membranes, drug delivery systems, hydrogels, water treatment, food packaging, etc. In this paper, some novel applications of this biopolymer in different fields are reviewed.

Bioconversion of chitin to chitosan: purification and characterization of chitin deacetylase from Mucor rouxii

Abstract: Chitin deacetylase, the enzyme that catalyzes the hydrolysis of acetamido groups of N-acetylglucosamine in chitin, has been purified to homogeneity from mycelial extracts of the fungus Mucor rouxii and further characterized. The enzyme exhibits a low pI (approximately 3). Its apparent molecular mass was determined to be approximately 75 kDa by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and approximately 80 kDa by size-exclusion chromatography, suggesting that the enzyme exists as a monomer. Carbohydrate analysis of purified chitin deacetylase revealed that the enzyme is a high-mannose glycoprotein and that its carbohydrate content is approximately 30% by weight. Chitin deacetylase is active on several chitinous substrates and chitin derivatives. The enzyme requires at least four N-acetylglucosamine residues (chitotetraose) for catalysis, and it is inhibited by carboxylic acids, particularly acetic acid. When glycol chitin (a water-soluble chitin derivative) was used as substrate, the optimum temperature for enzyme activity was determined to be approximately 50 degrees C and the optimum pH was approximately 4.5.