Characterization of chitinase from Exiguobacterium antarcticum and its bioconversion of crayfish shell into chitin oligosaccharides

Crayfish have become a heavily consumed food and its chitin-rich shell is of great value in terms of waste conversion. This study found a novel chitinase (EaChi40) from a marine bacterium Exiguobacterium antarcticum. The gene was cloned and expressed as a soluble protein of 40 kDa, having optimal activity at pH 6.0 and 30 ?. EaChi40 showed good stability and high specific activity, and kinetic studies found Km and Vmax were 0.86 mg/ mL and 13.66 mu mol/min/mg. For conversion crayfish shell into oligosaccharides, ball milling and ultrasound assisted hydrogen peroxide decolorization were applied to pretreat crayfish shell to facilitate its hydrolysis. After the enzymatic conversion, the hydrolysis products of chitobiose and N-acetyl-D-glucosamine were 9.09 mg/ mL and 9.21 mg/mL, respectively. EaChi40 efficiently degraded crayfish with a high hydrolysis rate of 76.1%. It is expected to be a good candidate for the production of chitin oligosaccharides in the food and biological fields.