, Volume 119, Issue 3, pp 229-240

Purification and characterization of an extracellular β-glucosidase with high transglucosylation activity and stability from Aspergillus niger No. 5.1

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Abstract

An extracellular β-glucosidase was extracted from the culture filtrate of Aspergillus niger No. 5.1 and purified to homogeneity by using ammonium sulfate precipitation, Chitopearl-DEAE chromatography, and Sephadex G-100 chromatography. The specific activity of the enzyme was enriched 6.33-fold, with a recovery of 11.67%. The enzyme was a monomer and the molecular mass was 67.5 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis and 66.5 kDa by gel-filtration chromatography. The enzyme had optimum activity at pH 6.0 and 60°C and was stable over the pH range of 3.0–9.0. It showed specificity of hydrolysis for p-nitrophenyl-β-d-glucoside and cellobiose. The K m and V max values of the enzyme for cellobiose and salicin were 5.34 mM, 2.57 µmol/(mL·s), and 3.09 mM, 1.34 µmol/(mL·s), respectively. Both amino acid composition and N-terminal amino acid sequence of the enzyme were determined, which provides useful information for cloning of this enzyme.