To promote the bioconversion of marine chitin waste into value-added products, we expressed a novel pH-stableMicromonospora aurantiaca-derived chitinase,MaChi1, inEscherichia coliand subsequently purified, characterized, and evaluated it for its chitin-converting capacity. Our results indicated thatMaChi1 is of the glycoside hydrolase (GH) family 18 with a molecular weight of approximately 57 kDa, consisting of a GH18 catalytic domain and a cellulose-binding domain. We recorded its optimal activity at pH 5.0 and 55 °C. It exhibited excellent stability in a wide pH range of 3.0–10.0. Mg2+(5 mM), and dithiothreitol (10 mM) significantly promotedMaChi1 activity.MaChi1 exhibited broad substrate specificity and hydrolyzed chitin, chitosan, cellulose, soluble starch, andN-acetyl chitooligosaccharides with polymerization degrees ranging from three to six. Moreover,MaChi1 exhibited an endo-type cleavage pattern, and it could efficiently convert colloidal chitin intoN-acetyl-D-glucosamine (GlcNAc) and (GlcNAc)2with yields of 227.2 and 505.9 mg/g chitin, respectively. Its high chitin-degrading capacity and exceptional pH tolerance makes it a promising tool with potential applications in chitin waste treatment and bioactive oligosaccharide production.
Lytic polysaccharide monooxygenases (LPMOs) are auxiliary redox enzymes crucial for the bioconversion of crystalline polysaccharides. This study presents the structural and functional characterization of a novel AA10 family LPMO, designated Ma LPMO10C, derived from Micromonospora aurantiaca . Recombinant Ma LPMO10C exhibited C1-specific oxidative cleavage activity against α -chitin and β -chitin. Notably, Ma LPMO10C displayed strong synergistic effects with its cognate chitinase Ma Chi1 through a sequential reaction, achieving 3.4– and 1.5–fold enhancements in the conversion efficiencies of α -chitin and β -chitin, respectively, compared with Ma Chi1 alone. Structural and physicochemical analyses revealed that Ma LPMO10C pretreatment enhances chitinase accessibility to the substrate by increasing amorphous regions, reducing crystallinity, and lowering the polymerization degree of chitin. When Ma LPMO10C pretreatment (1.50 U/mL, 24 h) was combined with Ma Chi1 hydrolysis (1.50 U/mL, 36 h), remarkable conversion yields of 67.5 % for α -chitin and 100 % for β -chitin to (GlcNAc) 2 and GlcNAc were achieved. The high catalytic efficiency and robust synergistic performance of Ma LPMO10C make it a promising biocatalyst for industrial-scale chitin processing.
危险品化学品经营许可证（带存储）