Characterization of a Novel Bi-functional Cold-Adapted Chitinase from Chitinibacter mangrovi FCG-7T for Efficient Production of N-acetyl-D-glucosamine

Cold-active chitinases that maintain robust catalytic performance at low temperatures are gaining attention as eco-friendly biocatalysts for energy-saving bioprocesses. In this study, a novel multifunctional chitinase of GH18 ( Cm Chi18B) was successfully cloned from a newly identified mangrove-associated bacterium Chitinibacter mangrovi FCG-7 T in Escherichia coli . The enzyme Cm Chi18B demonstrated adaptability to cold environments, retaining 55% of its maximal activity at 0°C. It displayed optimal activity at 55°C and pH 5.5. Cm Chi18B demonstrated high activity across a broad pH range of 4.0-12.0. Substrate hydrolysis analysis indicated that Cm Chi18B possesses bi-functional capabilities, including exochitinase and N-acetyl-β-D-glucosaminidase activities. After 24 h of incubation with colloidal chitin at 30°C, the enzyme achieved a N-acetyl-D-glucosamine (GlcNAc) conversion rate of 91.15% with a purity exceeding 98%. Intriguingly, the hydrolysis time for GlcNAc production varied with temperatures, with 0°C significantly impairing N-acetyl-β-glucosaminidase activity. These attributes position Cm Chi18B as a promising, low-energy biocatalyst for the sustainable production of GlcNAc and the valorization of chitin waste streams.