Heterologous expression of GH5 chitosanase in Pichia pastoris and antioxidant biological activity of its chitooligosacchride hydrolysate.

Chitosanase was widely used in the production of bioactive chitooligosacchride (CHOS) due to their safety, controllability, environmental protection, and biodegradability. Studies showed that the bioactivity of CHOS is closely related to its degree of polymerization. Therefore, the production of ideal polymerized CHOS becomes our primary goal. In this study, the glycosyl hydrolase (GH) family 5 chitosanase was successfully expressed heterologously in Pichia pastoris. After 96 h of high-density fermentation, the chitosanase activity reached 90.62 U·mL-1, the protein content reached 9.76 mg·mL-1. When 2% chitosan was hydrolyzed by crude enzyme (20 U/mL), the hydrolysis rate reached 91.2% after 8 h, producing a mixture of CHOS with 2-4 desirable degrees of polymerization (DP). Then, the antioxidant activity of CHOS mixture was investigated, and the results showed that the antioxidant effect was concentration-dependent and had great application potential in the field of nutrition.