Metaproteomics reveals enzymatic strategies deployed by anaerobic microbiomes to maintain lignocellulose deconstruction at high solids

Economically viable production of cellulosic biofuels requires operation at high solids loadings-on the order of 15 wt%. To this end we characterize Nature's ability to deconstruct and utilize mid-season switchgrass at increasing solid loadings using an anaerobic methanogenic microbiome. This community exhibits undiminished fractional carbohydrate solubilization at loadings ranging from 30 g/L to 150 g/L. Metaproteomic interrogation reveals marked increases in the abundance of specific carbohydrate-active enzyme classes. Significant enrichment of auxiliary activity family 6 enzymes at higher solids suggests a role for Fenton chemistry. Stress-response proteins accompanying these reactions are similarly upregulated at higher solids, as are beta-glucosidases, xylosidases, carbohydrate-debranching, and pectin-acting enzymes-all of which indicate that removal of deconstruction inhibitors is important for observed undiminished solubilization. Our work provides insights into the mechanisms by which natural microbiomes effectively deconstruct and utilize lignocellulose at high solids loadings, informing the future development of defined cultures for efficient bioconversion. Efficient solubilization of plant cell wall carbohydrates is required for microbial production of biofuels from lignocellulosic biomass. Here, the authors employ metaproteomics to interrogate enzymatic strategies of a methanogenic microbiome deconstructing switchgrass at increasing solids loading.

Automated summary

This study investigates the enzymatic strategies of a methanogenic microbiome deconstructing switchgrass at increasing solids loading, providing insights into the mechanisms of efficient lignocellulose utilization.