Lytic Polysaccharide Monooxygenases from Serpula lacrymans as Enzyme Cocktail Additive for Efficient Lignocellulose Degradation

Abstract

Lytic polysaccharide monooxygenase (LPMO) could oxidize and cleavage the glycosidic bonds of polysaccharides in lignocellulose, thereby promoting the hydrolysis of polysaccharide substrates by glycoside hydrolases and significantly improving the saccharification efficiency of lignocellulose. Brown-rot fungi are typical degraders of lignocellulose and contain multiple LPMO genes of the AA14 family and AA9 family, however, the AA14 LPMO from brown-rot fungi was rarely reported. Herein, the transcriptomic analysis of Serpula lacrymans incubated in the presence of pine exhibited that an AA14 LPMO (SlLPMO14A) was significantly upregulated and there were redox interactions between LPMOs and other enzymes (AA3, AA6, and hemicellulose degrading enzyme), indicating that SlLPMO14A may be involved in the degradation of polysaccharides. Enzymatic profiling of SlLPMO14A showed the optimal pH of 8.0 and temperature of 50 °C and it had higher reaction activity in the presence of 40% glycerol and acetonitrile. SlLPMO14A could significantly improve the saccharification of pine and xylan-coated cellulose substrate to release glucose and xylose by cellulase and xylanase by disturbing the surface structure of lignocellulose based on environmental scanning electron microscope and atomic force microscopy analysis.