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

[Display omitted] • A novel chitinase EaChi40 was isolated from Exiguobacterium sp., and its gene was expressed in E. coli BL21 (DE3). • Recombinant chitinase EaChi40 showed good cold-adapted catalysis and thermal stability. • Crayfish shell was treated with ball milling and ultrasonic-assisted decolorization to promote enzymatic hydrolysis. • EaChi40 effectively bio-transformed crayfish shell chitin by producing 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 °C. EaChi40 showed good stability and high specific activity, and kinetic studies found K m and V max were 0.86 mg/mL and 13.66 μmol/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. [ABSTRACT FROM AUTHOR]