Implementation of CDH in LPMO-Containing Minimal Cellulase Cocktails to Tune Bioproduct Production from Lignocellulosic Biomass

Abstract

Plant biomass can be converted to bioproducts using fungal enzymatic cocktails that have been improved by the implementation of lytic polysaccharide monooxygenases (LPMOs) known to boost cellulases. However, due to the complexity of their oxidative catalysis, it is still difficult to properly control and sustain LPMO activity. Here, we investigated whether the implementation of the natural enzymatic partner of LPMOs, i.e., cellobiose dehydrogenase (CDH), could be a promising solution. To this end, we reconstituted a minimal cocktail using the main cellulases from Trichoderma reesei and evaluated the impact of the addition of two LPMOs and one CDH on the conversion of wheat straw, miscanthus, pine, and poplar. Surprisingly, while the addition of LPMOs or LPMO/CDH showed little to no increase in glucose equivalent yields, the sole addition of CDH caused an increase of up to 27% (on miscanthus). Interestingly, CDH supplementation allowed tuning of the stream of degradation products toward cellobionic acid while maintaining equivalent yields or increasing the overall conversion yields in a biomass-dependent manner. Our study shows that extracting reasonable amounts of high-value-added oxidized sugars from industrial biomass is feasible, thereby opening new perspectives for the use of CDH in industry.