Hydrogen peroxide pretreatment efficiently assisting enzymatic hydrolysis of chitosan at high concentration for chitooligosaccharides

Chitooligosaccharides (COSs) have continuously attracted considerable attention as numerous biological activities. The highly efficient preparation of COSs, however, is still a challenge. In this paper, a clean two stage method is developed to hydrolyze chitosan at high concentration into COSs, comprising of pretreatment with hydrogen peroxide (H2O2) and hydrolysis with food-grade cellulase. The pretreatment reduced the viscosity of chitosan solution quickly, making more chitosan dissolving. Chitosan solution at high concentration (9%, w/v) was successfully prepared by fed-batch chitosan during the oxidative pretreatment. Within 6 h, the chitosan was enzymatically hydrolyzed to oligosaccharides with degree of polymerization (DP) of 2-9 and a small amount of monosaccharide, which was analyzed by thin layer chromatography (TLC) and MALDI-TOF MS. In addition, the results from FT-IR and NMR spectra demonstrated the chemical structure of degraded chitosan was not significantly altered. In summary, the two-stage method shows great potential in large-scale production of COSs. Besides, it is expected to couple with membrane bioreactor and immobilized enzyme technology to realize production of COSs with controlled molecular weight. (C) 2019 Elsevier Ltd. All rights reserved.