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Z. LIYAN1, Z. Qingxiao1, L. Zuowei2, and R. Hanming1. (1) Department of Food engineering, South China University of Technology, Wushan, Guangzhou, 510640, China, (2) Department of Food Science, Guangdong Industry Technical College, Guangzhou, 510300, China The oligomers of chitosan have been reported to exhibit distinct physiological activities. Application of those oligomers is very promising in the fields of functional foods, weight-loss diets and food additives. Chitosan oligomers can be prepared by an enzymatic method. Lysozyme can catalyze the hydrolysis of bacterial cell walls composed of alternating residues of (1-4)-linked N- acetylglucosamine and N-acetylmuramic acid. So it may hydrolyze chitosan (composed of (1-4)-linked N- acetylglucosamine and N-glucosamine) more rapidly than other non-specific enzymes. The objective of this paper was to research the effects of various factors (pH, temperature, degree of acetylation etc.) on lysozymic hydrolysis of chitosan, and the molecular weight (Mw) distribution of the hydrolysates obtained at optimal conditions. Lysozyme came from hen egg white. Chitosan was N-acetylated to prepare partially N-acetylated chitosans (PNACs). The amount of reducing sugar in solution was determined using the modification of Imoto T. method and used as the index of hydrolysis. The Mw distribution of hydrolysates was analyzed by GPC on a Waters 600 Controller apparatus. The results showed that the optimum temperature and pH of hydrolysis reaction were 55oC and 4.0, respectively. PNACs with N-acetylation degree of 30-35% showed higher digestibility by lysozyme. From time-course curves, at the initial stage (about 30min), the rate of hydrolysis was very rapid; after then, it slowed down. The amount of reducing sugar increased with the concentration of PNACs and lysozyme increasing. If the concentration of PNACs was 2.0%, the optimum E/S was 0.15. The GPC pattern showed that the Mw of hydrolysates ranged from 5,5kDa to 15kDa after PNACs were hydrolyzed at optimum conditions for 120h. The yield of oligomers obtained by lysozymic hydrolysis was large and the dispersity of Mw of the hydrolysis was little. As a result, Lysozyme could degrade chitosan to prepare oligomers with higher degree of polymerization.
Session 93, Carbohydrate: General
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