Investigating lytic polysaccharide monooxygenase-assisted wood cell wall degradation with microsensors

Lytic polysaccharide monooxygenase (LPMO) supports biomass hydrolysis by increasing saccharification efficiency and rate. Recent studies demonstrate that H2O2 rather than O-2 is the cosubstrate of the LPMO-catalyzed depolymerization of polysaccharides. Some studies have questioned the physiological relevance of the H2O2-based mechanism for plant cell wall degradation. This study reports the localized and time-resolved determination of LPMO activity on poplar wood cell walls by measuring the H2O2 concentration in their vicinity with a piezo-controlled H2O2 microsensor. The investigated Neurospora crassa LPMO binds to the inner cell wall layer and consumes enzymatically generated H2O2. The results point towards a high catalytic efficiency of LPMO at a low H2O2 concentration that auxiliary oxidoreductases in fungal secretomes can easily generate. Measurements with a glucose microbiosensor additionally demonstrate that LPMO promotes cellobiohydrolase activity on wood cell walls and plays a synergistic role in the fungal extracellular catabolism and in industrial biomass degradation. It is important to understand the enzymatic degradation of wood biomass by lytic polysaccharide monooxygenase, however, disagreements about the co-substrate exist. Here, the authors use piezo-controlled hydrogen peroxide micro-sensors to demonstrate that even low levels of hydrogen peroxide support the enzymatic degradation of wood cell walls.

Automated summary

This study demonstrates the activity of Lytic polysaccharide monooxygenase (LPMO) on wood cell walls and suggests that even low levels of hydrogen peroxide can support the enzymatic degradation of wood biomass. LPMO plays a synergistic role in fungal extracellular catabolism and industrial biomass degradation.