Expression and characterization of a cold-adapted, salt- and glucose-tolerant GH1 β-glucosidase obtained from Thermobifida halotolerans and its use in sugarcane bagasse hydrolysis

Abstract

A β-glucosidase obtained from Thermobifida halotolerans YIM 90462T was expressed in Escherichia coli BL21 and subsequently characterized. The recombinant enzyme ThBGL1A showed optimal activity at 45 °C and pH 6, but also showed high activity from 40 to 55 °C and pH 5.6–6.6. Its half-life activity was 58 min at 50 °C. ThBGL1A exhibited notable cold-adapted activity, retaining 13.1%, 49.4%, and 83.5% of its optimal activity at 5, 25, and 30 °C, respectively. Kinetic characterization revealed an enzymatic turnover (Kcat) of 30 s−1 (cellobiose), 41.8 s−1 (p-nitrophenyl-β-d-glucopyranoside), and 52.6 s−1 (p-nitrophenyl-β-d-galactopyranoside). Moreover, ThBGL1A had high tolerance for salt, xylose, and glucose, which are extremely desirable features for industrial applications. Interestingly, its Ki for glucose was 932 mM and more than 80% of its optimal activity in the presence of 2000 mM xylose. After the addition of ThBGL1A (0.05 mg/ml) to a commercial cellulase reaction system, glucose yields from sugarcane bagasse were increased 20% and 18% after 1 day at 30 °C and 45 °C, respectively. Overall, this work identifies a cold-adapted, salt- and glucose-tolerant β-glucosidase with potential applications in commercial cellulose utilization and the bioenergy industry.