Enzymatic production of diverse N-acetyl chitooligosaccharides employing a novel bifunctional chitinase and its engineered variants

Bioproduction of diverse N-acetyl chitooligosaccharides from chitin is of great value. In the study, a novel GH family 18 bifunctional chitinase gene (PsChi82) from Paenibacillus shirakamiensis was identified, expressed and biochemically characterized. PsChi82 was most active at pH 5.0, and 55 °C, and displayed remarkable pH stability with the broad pH range of 3.0–12.0. It showed high chitosanase activity of 10.6 U mg−1 and diverse hydrolysis products of GlcNAc, (GlcNAc)2, GlcN-GlcNAc and (GlcN)2-GlcNAc, which may facilitate comprehensively understanding of structure-function relationships of N-acetyl COSs. Three engineered variants were then expressed and characterized. Among them, PsChi82-CBM26 possessed specific activity of 25.1 U mg−1 against colloidal chitin, which was 2.1 folds higher than that of PsChi82. The diverse N-acetyl COSs were subsequently produced by PsChi82-CBM26 with a sugar content of 23.2 g L−1. These excellent properties may make PsChi82-CBM26 potentially useful for N-acetyl COSs production in the food and chemical industries. [Display omitted] •A novel bifunctional chitinase gene (PsChi82) was successfully expressed in E. coli.•The great pH stability and high chitosanase activity of PsChi82 were determined.•PsChi82 showed diverse hydrolysis products including two types of paCOSs.•Three engineered variants were designed, and PsChi82-CBM26 possessed high activity.•An efficient bioprocess for diverse N-acetyl COSs production was developed.