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

•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.