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

TL;DR

Scientists discovered a heat-loving enzyme from a Yellowstone hot spring microbe that efficiently breaks down plant compounds and could be useful in food and biofuel industries.

Contribution

A novel hyperthermophilic GH1 β-glucosidase from Acidilobus sp. with exceptional thermostability and ethanol tolerance is characterized and tested for glycoside hydrolysis.

Findings

BglAc shows maximum activity at 100 °C and pH 5.0 with pNPG as substrate.

The enzyme retains 96% activity in 10% ethanol and 78% in 20% ethanol.

BglAc effectively converts soybean isoflavone glycosides into their aglycones.

Abstract

A putative β-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 β-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-β-D-glucopyranoside (pNPG) 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, Km, Vmax, and Kcat/Km of BglAc toward pNPG were 357.62 U mg−1, 3.41 mM, 474.0 μmol min−1·mg−1, and 122.7 s−1mM−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 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.

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