Enzymes chitosan depolymerization

Muzzarelli, R.A.A., Tomasetti, M., and Ilari, P. 1994. Molecular parameters of chitosans depolymerized with the aid of papain. Enzyme Microb Technol. 16 110-114. 

By enzymatic means, chitosan can be easily depolymerized by a variety of hydrolases including lysozyme, pectinase, cellulases, hemicellulases, lipases and amylases, among others, thus showing a peculiar vulnerability to enzymes other than chitosanases [71-76]. While pectinase is of particular... 

Strong acids cleave C. into D- glucosamine (chitosa-mine) and acetic acid. On decomposition with alkalis, acetates and the weakly basic deacetylated, partially depolymerized, and crystallizable chitosan are formed the latter can form gels and films. The chiti-nases (EC 3.2.1.14) found in snail stomachs, some mold fungi, and bacteria can - like some lysozymes -dissolve C. The thus formed chitobiose, the disaccharide of P-1,4-linked NAG, is then cleaved to monomers by chitobiase (EC 3.2.1.30). Tlie formation of C. is catalyzed by the enzyme chitin synthase (EC 2.4.1.16). The activity of, e.g., the insecticide diflubenzurone is based on inhibition of this enzyme. 

Overcoming the problems of acid hydrolysis, scientists have adopted different enzymatic hydrolysis methods using different types of enzymes for the preparation of COS. The polysaccharide structure of the chitin or chitosan is converted to oligosaccharide form by specific enzymatic depolymerization or nonspecific enzymatic depolymerization. 

Currently, commercial chitin and chitosan are extracted from industrial shellfish processing wastes (shrimp, crab, lobster). The seasonal character of those raw materials and the variability of the composition of the organisms make the process of chitin extraction rather expensive with low reprodudbillty. Moreover, they are subjected to environmental variations that impact on the products supply and quality [14,40,116]. Chitin is extracted from crustacean shells by the use of strong adds and/or bases that can cause deacetylation and depolymerization of chitin [119]. Alternative methods include the use of enzymes or proteolytic microorganisms (e.g.. Pseudomonas malto-philia, Bacillus subtilis. Streptococcus faecium, Aspergillus oryzae) that hydrolyze shellfish proteins and leave the associated chitin intact [119]. 

Muzzarelli, R., Xia, W., Tomasetti, M., et al. (1995). Depolymerization of chitosan and substituted chitosans with the aid of a wheat germ lipase preparation. Enzyme Microbial TechnoL, 17, 541-545. 

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