Functional Metagenomics for Bioprospecting Novel Glycosyl Hydrolases in 2G Biofuel Production from Lignocellulosics

Abstract

Due to the rapid depletion of fossil fuel reserves, 2G biofuel production from lignocellulosics is considered as an alternative and sustainable energy source. Lack of economically viable and feasible bioprocess for lignocellulosic valorization hampers commercialization of 2G biofuels. For reducing carbon trade, countries like India are in the quest of replacing petroleum-based fuels to curtail greenhouse gas emissions and to boost circular economy (reduce and recycle). The enzymatic hydrolysis of cellulose and hemicellulose by glycosyl hydrolases (GHs) highlights the importance of cellulases and xylanases in the whole saccharification process. Currently, biorefineries demand robust biocatalysts (cellulases, hemicellulases) that can perform under extreme conditions of temperature, pH, or cations. A large number of GHs from different microorganisms have been explored. Still, there exists a huge gap between the available GHs and what is required by bioprocessing industries. Genetic and protein engineering techniques are not able to deliver industry-compatible extremophilic GHs. Considering the limitations of culture-dependent techniques, the combination of omics approaches with metagenomics is being explored for unraveling novel robust GHs from diverse environments. The chapter provides comprehensive insight to GHs and their structural and catalytic properties, expression patterns, and sequence identities. Furthermore, the chapter also summarizes the recent trends in metagenomics and its unleashing potential for unraveling GHs from extreme environments, which open new avenues in modern lignocellulosic-based biorefineries.