Deciphering the efficient cellulose degradation by the thermophilic fungus Myceliophthora thermophila focused on the synergistic action of glycoside hydrolases and lytic polysaccharide monooxygenases

The thermophilic fungus Myceliophthora thermophila as an efficient decomposer secretes various glycoside hy-drolases and auxiliary oxidation enzymes to deconstruct cellulose. However, the core enzymes critical for effi-cient cellulose degradation and their interactions with other cellulolytic enzymes remain unclear. Herein, the transcriptomic analysis of M. thermophila grown on Avicel exhibited that cellulases from GH5_5, GH6 and GH7, and lytic polysaccharide monooxygenases (LPMOs) from AA9 contributed to cellulose degradation. Moreover, the peptide mass fingerprinting analysis of major extracellular proteins and corresponding gene-knockout strains studies revealed that MtCel7A and MtCel5A were the core cellulolytic enzymes. Furthermore, synergistic ex-periments found that hydrolytic efficiencies of MtCel7A and MtCel5A were both improved by mixture C1/C4 oxidizing MtLPMO9H, but inhibited by C1 oxidizing MtLPMO9E and C4 oxidizing MtLPMO9J respectively. These results demonstrated the potential application of C1/C4 oxidizing LPMOs for future designing novel cellulolytic enzyme cocktails on the efficient conversion of cellulose into biofuels and biochemicals.

Automated summary

The thermophilic fungus Myceliophthora thermophila secretes various enzymes for cellulose degradation, including cellulases GH5_5, GH6, GH7, and lytic polysaccharide monooxygenases (LPMOs) AA9. The core cellulolytic enzymes were identified as MtCel7A and MtCel5A, and their hydrolytic efficiencies were improved by C1/C4 oxidizing LPMO9H but inhibited by C1 oxidizing LPMO9E and C4 oxidizing LPMO9J. These findings suggest the potential application of C1/C4 oxidizing LPMOs for efficient conversion of cellulose into biofuels and biochemicals.