Single-molecule study of oxidative enzymaticdeconstruction of cellulose

LPMO (lytic polysaccharide monooxygenase) represents a unique paradigm of cellulosicbiomass degradation by an oxidative mechanism. Understanding the role of LPMO indeconstructing crystalline cellulose is fundamental to the enzyme’s biological function andwill help to specify the use of LPMO in biorefinery applications. Here we show with real-timeatomic force microscopy that C1 and C4 oxidizing types of LPMO from Neurospora crassa(NcLPMO9F, NcLPMO9C) bind to nanocrystalline cellulose with high preference for the verysame substrate surfaces that are also used by a processive cellulase (Trichoderma reeseiCBH I) to move along during hydrolytic cellulose degradation. The bound LPMOs, however,are immobile during their adsorbed residence time ( ~ 1.0 min for NcLPMO9F) on cellulose.Treatment with LPMO resulted in fibrillation of crystalline cellulose and strongly ( ≥ 2-fold)enhanced the cellulase adsorption. It also increased enzyme turnover on the cellulose surface,thus boosting the hydrolytic conversion.