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

Abstract

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.