Expression and Molecular Modification of Chitin Deacetylase from Streptomyces bacillaris

Abstract

Chitin deacetylase can be used in the green and efficient preparation of chitosan from chitin. Herein, a novel chitin deacetylase <i>Sb</i>CDA from <i>Streptomyces bacillaris</i> was heterologously expressed and comprehensively characterized. <i>Sb</i>DNA exhibits its highest deacetylation activity at 35 °C and pH 8.0. The enzyme activity is enhanced by Mn²⁺ and prominently inhibited by Zn²⁺, SDS, and EDTA. <i>Sb</i>CDA showed better deacetylation activity on colloidal chitin, (GlcNAc)₅, and (GlcNAc)₆ than other forms of the substrate. Molecular modification of <i>Sb</i>CDA was conducted based on sequence alignment and homology modeling. A mutant <i>Sb</i>CDA63G with higher activity and better temperature stability was obtained. The deacetylation activity of <i>Sb</i>CDA63G was increased by 133% compared with the original enzyme, and the optimal reaction temperature increased from 35 to 40 °C. The half-life of <i>Sb</i>CDA63G at 40 °C is 15 h, which was 5 h longer than that of the original enzyme. The improved characteristics of the chitin deacetylase <i>Sb</i>CDA63G make it a potential candidate to industrially produce chitosan from chitin.