Biochemical and in silico structural properties of a thermo-acid stable β-glucosidase from Beauveria bassiana

Abstract

β-glucosidase hydrolyses the glycosidic bonds in cellobiose and cello-oligosaccharides, a critical step in the saccharification for biofuel production. Hence, the aim of this study was to gain insights into the biochemical and structural properties of a β-glucosidase from <i>Beauveria bassiana</i>, an entomopathogenic fungus. The β-glucosidase was purified to homogeneity using salt precipitation, ultrafiltration, and chromatographic techniques, attaining a specific activity of 496 U/mg. The molecular mass of the enzyme was then estimated via SDS-PAGE to be 116 kDa, while its activity pattern was confirmed by zymography using 4-methylumbelliferyl-β-d-glucopyranoside. Furthermore, the pH optima and temperature of the enzyme were found to be pH 5.0 and 60 °C respectively; its activity was significantly enhanced by Mg²⁺ and Na⁺ and was found to be relatively moderate in the presence of ethanol and dichloromethane. Molecular docking of the modelled <i>B. bassiana</i> β-glucosidase structure with the substrates, <i>viz</i>., 4-nitrophenyl β-d-glucopyranoside and cellobiose, revealed the binding affinity energies of -7.2 and -6.2 (kcal mol^-1), respectively. Furthermore, the computational study predicted Lys-657, Asp-658, and Arg-1000 as the core amino acid residues in the catalytic site of the enzyme. This is the first investigation into a purified β-glucosidase from <i>B. bassiana</i>, providing valuable insights into the functional properties of carbohydrases from entomopathogenic fungal endophytes.