Preparation of chitooligosaccharides by α-amylase from chitosan with oxidative pretreatment

Abstract

BACKGROUND: Chitooligosaccharides possess good physiological activity and a wide range of uses. In view of the difficulty in controlling the degree of polymerization of chitooligosaccharides prepared by chemical methods and the low efficiency of enzymatic methods, the preparation process of chitooligosaccharides prepared by H2O2 oxidation pretreatment combined with α-amylase catalysis was studied. RESULTS: Water-soluble chitosan was prepared by oxidation pretreatment of chitosan and then degradation by α-amylase. The enzymatic hydrolysis conditions were determined as follows: pH, 6.0; temperature, 60 °C; liquid–solid ratio, 5:1. The degree of polymerization of chitooligosaccharides prepared was adjusted by the amount of enzyme and hydrolysis time. The average degree of polymerization of chitooligosaccharides obtained was 5.4 when the amount of enzyme was 20 U g−1 for a hydrolysis time of 1.5 h. The results of infrared spectroscopy showed that the oxidative pretreatment and α-amylase degradation did not affect the molecular structure of the chitosan monomer. Using electrospray ionization mass spectrometry analysis, the degree of polymerization of the products was found to be mainly 2–8. CONCLUSIONS: H2O2 oxidative pretreatment can significantly improve the degradation efficiency of α-amylase, and the degree of polymerization of chitooligosaccharide products can be adjusted by regulating the hydrolysis conditions of the enzyme, which has ideal application prospects. © 2021 Society of Chemical Industry (SCI).