A novel β-glucosidase from a hot-spring metagenome shows elevated thermal stability and tolerance to glucose and ethanol

Abstract

β-glucosidase causes hydrolysis of β-1,4-glycosidic bond in glycosides and oligosaccharides. It is an industrially important enzyme owing to its potential in biomass processing applications. In this study, computational screening of an extreme temperature aquatic habitat metagenomic resource was done, leading to the identification of a novel gene, bglM, encoding a β-glucosidase. The comparative protein sequence and homology structure analyses designated it as a GH1 family β-glucosidase. The bglM gene was expressed in a heterologous host, Escherichia coli. The purified protein, BglM, was biochemically characterized for β-glucosidase activity. BglM exhibited noteworthy hydrolytic potential towards cellobiose and lactose. BglM, showed substantial catalytic activity in the pH range of 5.0–7.0 and at the temperature 40 °C–70 °C. The enzyme was found quite stable at 50 °C with a loss of hardly 20% after 40 h of heat exposure. Furthermore, any drastically negative effect was not observed on the enzyme’s activity in the presence of metal ions, non-ionic surfactants, metal chelating, and denaturing agents. A significantly high glucose tolerance, retaining 80% relative activity at 1 M, and 40% at 5 M glucose, and ethanol tolerance, exhibiting 80% relative activity in 10% ethanol, enrolled BglM as a promising enzyme for cellulose saccharification. Furthermore, its ability to catalyze the hydrolysis of daidzin and polydatin ascertained it as an admirably suited biocatalyst for enhancement of nutritional values in soya and wine industries.