Dual chitin and cellulose oxidative activity of the lytic polysaccharide monooxygenase CsAA15 from Cryptotermes secundus.

Lytic polysaccharide monooxygenases (LPMOs) offer a promising route to enhance the conversion of agricultural waste. Here, we characterized an Auxiliary Activities (AA) 15 family LPMO, CsAA15, derived from Cryptotermes secundus. We examined its binding affinity for cellulose and chitin, catalytic performance, optimal reaction conditions, and synergy with hydrolytic enzymes. The results showed that CsAA15 could effectively bind and oxidize crystalline cellulose and chitin, with optimal reaction temperature at 40-50 °C under acidic conditions. Thermal shift assay indicated that copper ion binding markedly increased the enzyme's thermal stability. Additionally, combining CsAA15 with commercial cellulase or chitinase significantly boosted substrate saccharification, raising soluble sugar release by approximately 1.4-fold. These findings established CsAA15 as a dual-substrate oxidative biocatalyst, providing a novel candidate for developing efficient and versatile enzymatic tools for biomass degradation.