Characterization of a Novel Hyperthermophilic GH1 -Glucosidase from Acidilobus sp. and Its Application in the Hydrolysis of Soybean Isoflavone Glycosides

A putative beta-glucosidase gene, BglAc, was amplified from Acidilobus sp. through metagenome database sampling from a hot spring in Yellowstone National Park. BglAc is composed of 485 amino acid residues and bioinformatics analysis showed that it belongs to the GH1 family of beta-glucosidases. The gene was successfully expressed in Escherichia coli with a molecular weight of approximately 55.3 kDa. The purified recombinant enzyme showed the maximum activity using p-nitrophenyl-beta-D-glucopyranoside (pNPG) as the substrate at optimal pH 5.0 and 100 degrees C. BglAc exhibited extraordinary thermostability, and its half-life at 90 degrees C was 6 h. The specific activity, K-m, V-max, and K-cat/K-m of BglAc toward pNPG were 357.62 U mg(-1), 3.41 mM, 474.0 mu mol min(-1).mg(-1), and 122.7 s(-1)mM(-1). BglAc exhibited the characteristic of glucose tolerance, and the inhibition constant Ki was 180.0 mM. Furthermore, a significant ethanol tolerance was observed, retaining 96% relative activity at 10% ethanol, and even 78% at 20% ethanol, suggesting BglAc as a promising enzyme for cellulose saccharification. BglAc also had a strong ability to convert the major soybean isoflavone glycosides (daidzin, genistin, and glycitin) into their corresponding aglycones. Overall, BglAc was actually a new beta-glucosidase with excellent thermostability, ethanol tolerance, and glycoside hydrolysis ability, indicating its wide prospects for applications in the food industry, animal feed, and lignocellulosic biomass degradation.