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

A putative β-glucosidase gene, , was amplified from 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 β-glucosidases. The gene was successfully expressed in with a molecular weight of approximately 55.3 kDa. The purified recombinant enzyme showed the maximum activity using -nitrophenyl-β-D-glucopyranoside (NPG) as the substrate at optimal pH 5.0 and 100 °C. BglAc exhibited extraordinary thermostability, and its half-life at 90 °C was 6 h. The specific activity, , , and / of BglAc toward NPG were 357.62 U mg, 3.41 mM, 474.0 μmol min·mg, and 122.7 smM. BglAc exhibited the characteristic of glucose tolerance, and the inhibition constant i 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 β-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.