Characterization of a thermostable cellobiose dehydrogenase from Myceliophthora thermophila and its function of electron‐donating for lytic polysaccharide monooxygenase

Abstract

Cellobiose dehydrogenase (CDH) catalyzes the oxidation of cello‐oligosaccharides and transfers electrons to oxygen or other electron receptors, such as lytic polysaccharide oxygenases (LPMOs). Cellobiose dehydrogenase has the potential to be used as an electron donor for LPMOs. Therefore, it is important to obtain CDHs under reaction conditions that are compatible with those of cellulases and LPMOs. Here, a CDH gene from Myceliophthora thermophila (MtCDH‐A) was constitutively expressed in Trichoderma reesei, and its ability to donate electrons to the LPMO was validated. MtCDH‐A has an optimal pH of 6.0 and maintains relatively high activity over a wide pH range. The optimal temperature was 60°C, and it remained stable at 50°C for a long time. These enzymatic properties were compatible with the catalytic conditions of fungal LPMOs and cellulases. When MtCDH‐A was used as an electron donor, the synergistic effect of LPMO and cellulase improved the degradation efficiency of phosphoric acid‐swollen cellulose by 141%. This work provides a novel insight into finding a stable electron donor for LPMOs and a new direction for finding more efficient thermostable CDHs in newly identified fungal species. © 2023 Society of Industrial Chemistry and John Wiley & Sons Ltd.