Chitosan is a functional ingredient that is widely used in food chemistry as an emulsifier, flocculant, antioxidant, or preservative. Chitin deacetylases (CDAs) can catalyze the hydrolysis of acetyl groups, making them useful in the clean production of chitosan. However, the high inactivity of crystalline chitin catalyzed by CDAs has been regarded as the technical bottleneck of crystalline chitin deacetylation. Here, we mined the AsCDA gene from the genome of Acinetobacter schindleri MCDA01 and identified a member of the uraD_N-term-dom superfamily, which was a novel chitin deacetylase with the highest deacetylation activity. The AsCDA gene was expressed in Escherichia coli BL21 by IPTG induction, whose activity to colloidal chitin, α-chitin, and β-chitin reached 478.96 U/mg, 397.07 U/mg, and 133.27 U/mg, respectively. In 12 h, the enzymatic hydrolysis of AsCDA removed 63.05% of the acetyl groups from α-chitin to prepare industrial chitosan with a degree of deacetylation higher than 85%. AsCDA, as a potent chitin decomposer in the production of chitosan, plays a positive role in the upgrading of the chitosan industry and the value-added utilization of chitin biological resources.
Keywords: Acinetobacter schindleri; chitin deacetylase; chitosan; crystalline chitin; uraD_N-term-dom superfamily.