Preparation of glucosamine by hydrolysis of chitosan with commercial α-amylase and glucoamylase

In order to overcome the defects of chemical hydrolysis approach to prepare glucosamine, an enzymatic hydrolysis method was developed. Glucosamine was prepared by hydrolyzing chitosan, employing alpha-amylase initially, and subsequently, glucoamylase. The optimal hydrolyzing conditions were as follows: reaction time, 4 h; pH, 5.0; temperature, 50 A degrees C; and, alpha-amylase, 80 U/g for the initial reaction. Subsequently, glucoamylase was added in the presence of alpha-amylase. The optimal reaction conditions were found to be: reaction time, 8 h; pH, 4.5; temperature, 55 A degrees C; and, glucoamylase, 4 000 U/g. The hydrolysates were subject to filtrating, concentrating to about 20% (w/w), precipitating with five volumes of ethanol, and drying at 60 A degrees C for 2 h. The content and the yield of glucosamine in the dried precipitate were 91.3% (w/w) and 86.2% (w/w), respectively. The method developed in this study is a promising option in the preparation of glucosamine.