Rice (Oryza sativa L.) straw, an agricultural waste of high yield, is a sustainable source of fermentable sugars for biofuel and other chemicals. However, it shows recalcitrance to microbial catalysed depolymerization. We herein describe development of thermotolerant microbial consortium (RSV) from vermicompost with ability to degrade rice straw and analysis of its metagenome for bacterial diversity, and lignocellulolytic carbohydrate active enzymes (CAZymes) and their phylogenetic affiliations. RSV secretome exhibited cellulases and hemicellulases with higher activity at 60 °C. It catalysed depolymerization of chemical pretreated rice straw as revealed by scanning electron microscopy and saccharification yield of 460 mg g−1 rice straw. Microbial diversity of RSV was distinct from other compost habitats, with predominance of members of phyla Firmicutes, Proteobacteria and Bacteroidetes; and Pseudoclostridium, Thermoanaerobacterium, Chelatococcus and Algoriphagus being most abundant genera. RSV harboured 1389 CAZyme encoding ORFs of glycoside hydrolase, carbohydrate esterase, glycosyl transferase, carbohydrate binding module and auxiliary activity functions. Microorganisms of Firmicutes showed central role in lignocellulose deconstruction with importance in hemicellulose degradation; whereas representatives of Proteobacteria and Bacteroidetes contributed to cellulose and lignin degradation, respectively. RSV consortium could be a resource for mining thermotolerant cellulolytic bacteria or enzymes and studying their synergism in deconstruction of chemically pretreated rice straw.

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Background Astilbe rivularis L. is an indigenous medicinal plant growing in high altitude of Darjeeling Himalayan region of India and Nepal. The plant rhizome has been used traditionally as medicine by local tribes to treat various ailments including infectious and other diseases. The present study aims to evaluate the plant rhizome for chemical composition and in vitro antioxidant, antibacterial and cytotoxic bioactivities. Methods The methanolic extract of rhizome was analyzed for phytochemical constituents by biochemical and GC-MS methods. The antibacterial property of the extract was monitored by agar well diffusion assay. Antioxidant potential was assessed by in vitro DPPH and ABTS scavenging assays and scavenging of induced ROS in normal cell line using fluorescent probe 2′, 7′- dichlorofluorescin diacetate. Cytotoxic effect of the extract in cancer and normal cell lines was determined by MTT assay. Results Rhizome methanolic extract contained terpenoids, flavonoids, tannins, phenols, alkaloids, saponins and reducing sugars. Further analysis of extract by GC-MS showed the presence of nine major constituents belonging to terpenoids and fatty acid groups. The extract had marked in vitro ROS scavenging activity and moderate antibacterial activity against gram positive and gram negative bacteria. It showed cytotoxicity to neuroblastoma (SHSY5Y) cell line with IC 50 value < 100 μg ml − 1 but had least damaging effect on normal cells, like human embryonic kidney (HEK-293) and liver (WRL-68) cell lines. Conclusion The study suggests that Astilbe rivularis has potential as source of new potent antibacterial, antioxidant and anticancer agents. Further studies on purification and characterization of active compounds from Astilbe rivularis and their biological evaluation are highly recommended.

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