Bioprospecting metagenomics of a microbial community on cotton degradation: Mining for new glycoside hydrolases

Glycoside hydrolases (GHases) of higher performance are immediately needed for efficient degradation of plant biomass into fermentable sugars in industrial processes. The current study represents functional characterization of the enzymatic repertoire involved in crude cotton biomass degradation. Physical contact between cells and substrate is necessary for efficient hydrolysis of cellulose. Cytophagales, which plays a major role in cotton biomass decomposition, was identified as a prevalent community member by 16 S rRNA analysis. From the metagenome data, 2058 GHase homologs were identified, of which sixteen were successfully expressed in E. coli. Four enzymes showed activities on p-nitrophenyl-β-d-xylopyranoside, four showed activities on p-nitrophenyl-β-d-glucopyranoside, two had activities against p-nitrophenyl-β-d-glucuronide, one showed activity on laminarin, three had activities against p-nitrophenyl-N-acetyl-β-d-glucosaminide, one had activity towards carboxymethyl cellulose, and one towards p-nitrophenyl-β-d-mannopyranoside. Metagenomics provides a good resource for mining novel biomass degrading enzymes. The sixteen GHases that were cloned may have potential application for biomass conversion and bioproduct production. Functional characterization of the enzymatic repertoire in cotton biomass degradation and analysis of the GHases provide insight into the composition and interaction of enzymes and pathways of plant biomass degradation.