Functional characterization of thermotolerant microbial consortium for lignocellulolytic enzymes with central role of Firmicutes in rice straw depolymerization

Abstract

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.

Characterization of Thermophilic Lignocellulolytic Microorganisms in Composting

“…Consequently, this group should play a crucial role in the breakdown of HC during the entire process. Similar conclusions have been obtained using metagenomics analysis ( Antunes et al, 2016 ; Gavande et al, 2021 ). Furthermore, it was noticeable that many bacterial isolates having the same accession number showed different thermal phenotypes at the stages of composting or even at the same stage ( Table 2 ).…”

“…In some cases, an approximation at the genus or even species level has been possible, showing a detailed profile of the microbiome of the composting piles, extremely dependent on the RMs and the operating conditions applied in each case ( Langarica-Fuentes et al, 2014 ; Estrella-González et al, 2020 ; Ince et al, 2020 ). Other authors have described the capacities of microbial consortia from the “secretome” of lignocellulosic materials subjected to different thermal treatments, suggesting a metabolic coordination between different species with a view to deconstruction of the lignocellulose ( Gavande et al, 2021 ). In any case, most of the studies described, although novel because they are based on the use of genomic mining and powerful data platforms, do not allow knowing the thermal tolerance range of the identified taxa, nor the actual capacity to deconstruct lignocellulosic fractions.…”

Thermoxylanolytic and Thermosaccharolytic Potential of a Heat Adapted Bacterial Consortium Developed From Goat Rumen Contents

“…Among the various xylanolytic enzymes produced by RSC, endoxylanase exhibited maximum activity. Previous studies on the production of cellulolytic enzymes by bacterial consortia developed from compost (Zhu et al, 2016) and vermicompost (Gavande et al, 2021) also showed relatively higher proportion of endoxylanase activity.…”

“…Following this, the plate was stained with Congo Red solution (0.1% v/v) for 15 min and destained with 1M NaCl. Plates were visualized for zones of clearance and hydrolysis capacity was calculated (Gavande et al, 2021).…”

Recent Advancements in Microbial Polysaccharides: Synthesis and Applications

“…Depolymerizing enzymes are being utilized in the process of in vitro depolymerization and as instruments for studying the chemical composition [ 73 , 74 ]. During in vitro synthesis, carbohydrate sulfotransferases and other replacement grafting enzymes, including acetate kinase, could be used to attach or remove substituents that are of critical interest to the molecule’s final bioactivity [ 75 ].…”