Enzymatic preparation of chitooligosaccharides by commercial lipase

The effect of a commercial lipase on chitosan degradation was investigated. When four chitosans with various degrees of deacetylation were used as substrates, the lipase showed higher optimal pH toward chitosan with higher DD (degree of deacetylation). The optimal temperature of the lipase was 55 degrees C for all chitosans. The enzyme exhibited higher activity to chitosans which were 82.8% and 73.2% deacelylated. Kinetics experiments show that chitosans with DO of 82.8% and 73.2% which resulted in lower K(m) values had stronger affinity for the lipase. The chitosan hydrolysis carried out at 37 degrees C produced larger quantity of COS (chitooligosaccharides) than that at 55 degrees C when the reaction time was longer than 6 h, and COS yield of 24 h hydrolysis at 37 degrees C was 93.8%. Products analysis results demonstrate that the enzyme produced glucosamine and chitooligosaccharides with DP (degree of polymerization) of 2-6 and above, and it acted on chitosan in both exo- and enclo-hydrolytic manner. (C) 2008 Published by Elsevier Ltd.