Insights into the H₂O₂-Driven Lytic Polysaccharide Monooxygenase Activity on Efficient Cellulose Degradation in the White Rot Fungus Irpex lacteus

Abstract

In contrast to O2, H2O2 as the cosubstrate for lytic polysaccharide monooxygenases (LPMOs) exhibits great advantages in industrial settings for cellulose degradation. However, H2O2-driven LPMO reactions from natural microorganisms have not been fully explored and understood. Herein, secretome analysis unraveled the H2O2-driven LPMO reaction in the efficient lignocellulose-degrading fungus Irpex lacteus, including LPMOs with different oxidative regioselectivities and various H2O2-generating oxidases. Biochemical characterization of H2O2-driven LPMO catalysis showed orders of magnitude improvement in catalytic efficiency compared to that of O2-driven LPMO catalysis for cellulose degradation. Significantly, H2O2 tolerance of LPMO catalysis in I. lacteus was an order of magnitude higher than that in other filamentous fungi. In addition, natural reductants, gallic acid, in particular, presented in lignocellulosic biomass could sufficiently maintain LPMO catalytic reactions. Moreover, the H2O2-driven LPMO catalysis exhibited synergy with canonical endoglucanases for efficient cellulose degradation. Taken together, these findings demonstrate the great application potential of the H2O2-driven LPMO catalysis for upgrading cellulase cocktails to further improve cellulose degradation efficiency.