Background:Efficient deconstruction of lignocellulosic biomass into simple sugars in an economically viable man‑ner is a prerequisite for its global acceptance as a feedstock in bioethanol production. This is achieved in nature by suites of enzymes with the capability of efficiently depolymerizing all the components of lignocellulose. Here, we provide detailed insight into the repertoire of enzymes produced by microorganisms enriched from the gut of the crop pathogen rice yellow stem borer (Scirpophaga incertulas).Results:A microbial community was enriched from the gut of the rice yellow stem borer for enhanced rice straw degradation by sub‑culturing every 10days, for 1year, in minimal medium with rice stra... More
Background:Efficient deconstruction of lignocellulosic biomass into simple sugars in an economically viable man‑ner is a prerequisite for its global acceptance as a feedstock in bioethanol production. This is achieved in nature by suites of enzymes with the capability of efficiently depolymerizing all the components of lignocellulose. Here, we provide detailed insight into the repertoire of enzymes produced by microorganisms enriched from the gut of the crop pathogen rice yellow stem borer (Scirpophaga incertulas).Results:A microbial community was enriched from the gut of the rice yellow stem borer for enhanced rice straw degradation by sub‑culturing every 10days, for 1year, in minimal medium with rice straw as the main carbon source. The enriched culture demonstrated high cellulolytic and xylanolytic activity in the culture supernatant. Metatranscrip‑tomic and metaexoproteomic analysis revealed a large array of enzymes potentially involved in rice straw deconstruc‑tion. The consortium was found to encode genes ascribed to all five classes of carbohydrate‑active enzymes (GHs, GTs, CEs, PLs, and AAs), including carbohydrate‑binding modules (CBMs), categorized in the carbohydrate‑active enzymes (CAZy) database. The GHs were the most abundant class of CAZymes. Predicted enzymes from these CAZy classes have the potential to digest each cell‑wall components of rice straw, i.e., cellulose, hemicellulose, pectin, callose, and lignin. Several identified CAZy proteins appeared novel, having an unknown or hypothetical catalytic counterpart with a known class of CBM. To validate the findings, one of the identified enzymes that belong to the GH10 family was functionally characterized. The enzyme expressed in E. coli efficiently hydrolyzed beechwood xylan, and pretreated and untreated rice straw.Conclusions:This is the first report describing the enrichment of lignocellulose degrading bacteria from the gut of the rice yellow stem borer to deconstruct rice straw, identifying a plethora of enzymes secreted by the microbial com‑munity when growing on rice straw as a carbon source. These enzymes could be important candidates for biorefiner‑ies to overcome the current bottlenecks in biomass processing.Keywords:Rice yellow stem borer, Gut consortium, Microbial diversity, Targeted enrichment, Metaexoproteome, Carbohydrate‑active enzymes, Xylanase, GH10 family
