Chitin,present in crustacean shells,insects,and fungi,is the second most plentiful natural organic fiber after wood.To effectively use chitin in a cost-saving and environmentally friendly way in aquaculture,crustacean shells (e.g.,shrimp-shell meal) are supplemented into aquafeed after degradation by chemical methods.Herein,we describe a chitinase from Aeromonas veronii B565,designated ChiB565,,which potently degrades shrimp-shell chitin and resists proteolysis.,We isolated recombinant ChiB565 of the expected molecular,mass in large yield from Pichia pastoris.ChiB565 is optimally,active at pH 5.0 and 50 °C and stable between pH 4.5 and,9.0 at 50 °C and below.