Abstract
A novel β-glucosidase gene (PtBglu1) from the thermophilic fungus, Paecilomyces thermophila, was cloned and expressed in Pichia pastoris. PtBglu1 contained an open reading frame of 1440-bp nucleotides and encoded a protein of 479 amino acids which showed significant similarity to other fungal β-glucosidases from glycoside hydrolase (GH) family 1. The recombinant β-glucosidase (PtBglu1) was secreted at high level of 190.2UmL−1 in high cell density fermentor (5L). PtBglu1 was purified to homogeneity, and was found to be a glycoprotein with molecular mass of 56.7kDa. The purified PtBglu1 showed optimum catalytic activity at pH 6.0 and 55°C. The enzyme exhibited broad substrate specificity with highest activity toward pNP-β-d-glucopyranoside, followed by pNP-β-d-galactopyranoside and cellobiose. The Km values for pNP-β-d-glucopyranoside, cellobiose, gentiobiose and salicin were 0.55mM, 1.0mM, 1.74mM and 6.85mM, respectively. These properties make PtBglu1 a potential candidate for various industrial applications.
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