Characterization of a lytic polysaccharide monooxygenase important for utilization of chitin in Chitinibacter mangrovi FCG-7.

Lytic polysaccharide monooxygenases (LPMOs) are crucial for recalcitrant biomass degradation. We characterized CmLPMO10, an AA10 LPMO from Chitinibacter mangrovi FCG-7, and demonstrated its essential role in α-chitin utilization through transcriptomics and gene deletion. Biochemically, CmLPMO10 is a robust enzyme with optimal activity at 50 °C and pH 7.0, featuring unique regioselectivity: C1-specific oxidative activity on chitin and C1/C4 activity on cellulose. CmLPMO10 showed the strongest synergistic degradation of α-chitin with its homologous chitinase CmChi18B (degree of synergy: 1.96). Furthermore, CmLPMO10 also exhibited synergistic enhancement of cellulosic substrate hydrolysis when combined with the commercial cellulase preparation Celluclast® 1.5 L, achieving degree of synergy values of 1.31 for Avicel, 1.24 for PASC, and 1.55 for sugarcane bagasse-derived cellulose. Structural analysis revealed CmLPMO10 pretreats α-chitin not by forming pores but by inducing surface roughening, loosening, and selective crystallinity reduction to enhance substrate accessibility. The collaboration is finely tuned, with optimal enzyme ratios differing between chitinase partners (1:5 for CmChi18B; 1:25 for SmChiC), and exhibits nonlinear kinetics reflecting synergy-competition balance. Our work elucidates the function and mechanism of CmLPMO10 and its potential as a key biocatalyst for efficient α-chitin biomass valorization.