Characterisation of symbiotic cellulolytic microbial consortium enriched on napier grass

Cooperative interactions of bacteria plays an important role on decomposition of complex lignocellulosic plant biomass which provides a basis on carbon cycling in nature and conversion of biomass to fuels and chemicals in biorefineries. In this study, active lignocellulose degrading microbial consortium was constructed from microflora originated from forest compost soil by successive subcultivation on napier grass under facultative anoxic conditions. The structurally stable enriched consortia comprised mainly Proteobacteria, Firmicutes, and Bacteroidetes according to tagged 16S rRNA gene amplicon sequencing. Changes in the microcosm structure was found during batch cultivation of the consortium with increasing abundance of facultative Proteobacteria in the middle of incubation period which was then subsequently replaced by Firmicutes and Bacteroidetes along with dynamic change in CMCase, xylanse, and ß-glucanase activity profile in the supernatant. The consortium was highly active on degradation of alkaline pretreated lignocellulosic substrates with more than 50% reduction in solid biomass after incubation at 40 oC for 10 d. Direct shotgun sequencing of the MQSc metagenomes revealed an abundance of genes encoding for various lignocellulose degrading enzymes in 23 glycosyl hydrolase (GH) families. Various enzymes attacking the main-chain and side-chain of cellulosic and hemicellulosic were dominated by GH2, 3, 5, 9, 10, 26, 28 and 43, reflecting adaptation of the enzyme systems to the herbaceous substrate. The complex structurally stable consortium is a platform for discovering potential lignocellulose degrading enzymes for biotechnological applications.