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

Objective： In order to overcome the defects of chemical hydrolysis approach to prepare glucosamine, an enzymatic hydrolysis method was developed. Methods： Glucosamine was prepared by hydrolyzing chitosan, em- ploying e-amylase initially, and subsequently, glucoamylase. Results： The optimal hydrolyzing conditions were as follows： reaction time, 4 h; pH, 5.0; temperature, 50 ℃; and, α-amylase, 80 U/g for the initial reaction. Subsequently, glucoamylase was added in the presence of a-amylase. The optimal reaction conditions were found to be： reaction time, 8 h; pH, 4.5; temperature, 55 ℃; and, glucoamylase, 4000 U/g. The hydrolysates were subject to filtrating, concentrating to about 20% （w/w）, precipitating with five volumes of ethanol, and drying at 60 ℃ 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. Conclusions： The method developed in this study is a promising option in the preparation of glucosamine.