Bioconversion of chitin into chitin oligosaccharides using a novel chitinase with high chitin-binding capacity

Abstract

Chitin is the second largest renewable biomass resource in nature, it can be enzymatically degraded into high-value chitin oligosaccharides (CHOSs) by chitinases. In this study, a chitinase (ChiC8–1) was purified and biochemically characterized, its structure was analyzed by molecular modeling. ChiC8–1 had a molecular mass of approximately 96 kDa, exhibited its optimal activity at pH 6.0 and 50 °C. The Km and Vmax values of ChiC8–1 towards colloidal chitin were 10.17 mgmL−1 and 13.32 U/mg, respectively. Notably, ChiC8–1 showed high chitin-binding capacity, which may be related to the two chitin binding domains in the N-terminal. Based on the unique properties of ChiC8–1, a modified affinity chromatography method, which combines protein purification with chitin hydrolysis process, was developed to purify ChiC8–1 while hydrolyzing chitin. In this way, 9.36 ± 0.18 g CHOSs powder was directly obtained by hydrolyzing 10 g colloidal chitin with crude enzyme solution. The CHOSs were composed of 14.77–2.83 % GlcNAc and 85.23–97.17 % (GlcNAc)2 at different enzyme-substrate ratio. This process simplifies the tedious purification and separation steps, and may enable its potential application in the field of green production of chitin oligosaccharides.