A Novel Highly Thermostable Multifunctional Beta-Glycosidase from Crenarchaeon Acidilobus saccharovorans

We expressed a putative β-galactosidase Asac_1390 from hyperthermophilic crenarchaeon Acidilobus saccharovorans in Escherichia coli and purified the recombinant enzyme. Asac_1390 is composed of 490 amino acid residues and showed high sequence similarity to family 1 glycoside hydrolases from various thermophilic Crenarchaeota. The maximum activity was observed at pH 6.0 and 93°C. The half-life of the enzyme at 90°C was about 7 hours. Asac_1390 displayed high tolerance to glucose and exhibits hydrolytic activity towards cellobiose and various aryl glucosides. The hydrolytic activity with p-nitrophenyl (pNP) substrates followed the order pNP-β-D-galactopyranoside (328 U mg(-1)), pNP-β-D-glucopyranoside (246 U mg(-1)), pNP-β-D-xylopyranoside (72 U mg(-1)), and pNP-β-D-mannopyranoside (28 U mg(-1)). Thus the enzyme was actually a multifunctional β-glycosidase. Therefore, the utilization of Asac_1390 may contribute to facilitating the efficient degradation of lignocellulosic biomass and help enhance bioconversion processes.