Binding Stability and Catalytic Mechanism of a Novel Chitin Deacetylase from Cytobacillus firmus and Preparation of Chitosan

This study reports the heterologous expression, purification, and functional characterization of a novel chitin deacetylase (CDA) from Cytobacillus firmus. The recombinant CfCDA exhibited optimal activity at pH 7 and 35 °C, with Mg2+ enhancing its function. Deep eutectic solvent (DES) pretreatment significantly improved chitin accessibility, enabling CfCDA to produce chitosan with a high degree of deacetylation (71.2%) and recovery rate (14.2%). Structural analyses confirmed reduced crystallinity and successful acetyl removal. Molecular docking and dynamics simulations identified Asp318, His470, and Trp433 as key catalytic residues with stable binding to (GlcNAc)4. These findings highlight CfCDA's potential for eco-friendly chitosan production and provide a basis for future enzyme engineering.