Biochemical characterization of a novel thermostable beta-glucosidase from Dictyoglomus turgidum

Dtur_0462 gene from the hypertermophilic bacterium Dictyoglomus turgidum, encoding a beta-glucosidase, was synthetically produced and expressed in Escherichia coli BL21(DE3)-RIL. Dtur beta Glu was purified to homogeneity by affinity chromatography and its homotetrameric structure was determined by gel filtration. The monomer is composed by 418 amino acidic residues and showed high sequence similarity with Glycoside Hydrolases (GHs) belonging to GH1 family. The maximum activity of Dtir beta Glu was observed at 80 degrees C and at pH 5.4.DturKlu was stable in the range of pH 5-8 and retained 70% of its activity after 2 h of incubation at 70 degrees C. Metal ions and chemical reagents differently influenced the beta-glucosidase activity; furthermore, Dtur beta Glu displays a good ethanol and glucose tolerance (K-i 750 mM). The enzyme is active on p-nitrophenyl-beta-D-glucopyranoside (pNPGIu) (K-m 0.84 mM) and p-nitrophenyl-beta-D-galactopyranoside (pNPGal) (K-m 136 mM) and shows a broad substrate specificity towards natural compounds as salicin, cellobiose and genistin. The ability to hydrolyze different substrates, the activation in the presence of surfactants, the good thermal resistance, and finally the high glucose and ethanol tolerance make this enzyme a good candidate for industrial applications. (C) 2018 Elsevier B.V. All rights reserved.