Chitin, the second most abundant natural polysaccharide, is a renewable resource with great potential for producing functional oligosaccharides. In this study, we identified and characterized CtChi70, a glycoside hydrolase family 18 (GH18) exochitinase that selectively hydrolyzes chitin to produce N -acetyl chitobiose [(GlcNAc)₂] with exceptional purity (≥98 %). CtChi70 was heterologously expressed in Escherichia coli CtChi70 at a high yield of 228.2 ± 47.8 mg L −1 . The purified enzyme exhibited optimal activity at pH 5.0 and 45 °C, and demonstrated stability across a broad pH range (4.0–12.0). Time-course hydrolysis of colloidal chitin showed moderate catalytic efficiency but high product specificity, peaking at 24 h with minimal N -acetylglucosamine byproduct. The ability of CtChi70 to directly convert raw chitin powder to high-purity (GlcNAc)₂ suggests its potential for applications requiring pure chitooligosaccharides. These findings highlight CtChi70 as a promising biocatalyst for sustainable chitin valorization.
Chenxi Gu,Liyan Yang,Susu Han,Dengfeng Yang,Xiaodong Xu,WenChao Zhang,Mingguo Jiang,Lixia Pan
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.
危险品化学品经营许可证（带存储）