Eukaryotic expression of chitinase from dark sleeper (Odontobutis potamophila) and its effects on growth and immunity.

Chitinase, an enzyme that hydrolyzes β-1,4-glycosidic bonds to degrade chitin, is essential for the digestion of chitin in fish. In this study, the chitinase OpCht from Odontobutis potamophila was expressed in Pichia pastoris, and its enzymatic properties and functional effects were evaluated. The findings revealed that OpCht exhibited optimal activity at pH 6.0 and 50 °C, with stability in the pH range of 4-8 and temperatures from 4 to 40 °C. K⁺, Na⁺, Ca²⁺, Mg²⁺, Mn²⁺, Hg²⁺, and Al³⁺ showed varying degrees of activation on the enzyme. At the end of the 8-week trial, the addition of OpCht significantly increased the height of intestinal villi and the thickness of the muscular layer, leading to significantly weight in the treated groups. The alleviation of intestinal inflammation also resulted in an increased survival rate (SR) of O. potamophila. High concentration treatment groups (2, 4 μg/g) showed significantly elevated digestive enzyme activities, as well as increased antioxidant enzyme activities and immune parameters. These results demonstrate that the P. pastoris expression system has successfully produced the chitinase OpCht from O. potamophila, and the addition of a certain concentration of OpCht can promote fish growth and enhance immune functions, offering a promising enzyme preparation for the aquaculture industry.