Purification and Characterization of Thermostable Acidic β-Glucosidase from Aspergillus niger L.

Abstract

Abstract: In this study, an acidic β-glucosidase (BGL) was purified from acid-tolerant Aspergillus niger L. mycelia by ethanol precipitation, DEAE-Sepharose column chromatography and Sephadex G-100 column chromatography. SDS-PAGE showed that the molecular weight of the enzyme was 125.7 kD. Further characterization revealed that it had maximal hydrolytic activity on p-nitrophenyl-β-D-glucopyranoside (pNPG) at pH 3.0 — 4.0 and 70 ℃ with a Km of 2.35 mmol/L and a kcat/Km of 2.99 × 104 mol/L·s. The kcat/Km values for hydrolyzing geniposide and salicin were 1.26 × 104 L/(mol·s) and 1.37 × 104 L/(mol·s), respectively. The hydrolytic activity was activated obviously by Mn2+ but inhibited faintly by Fe2+, Zn2+ and Cu2+. The BGL was highly stable at pH 2.0 — 8.5, and 85% of its original activity could be maintained after 60 min of heat treatment at 65 ℃. Thus, the enzyme was highly stable to heat.

Key words: intracellular enzyme, ethanol precipitation, p-nitrophenyl-β-D-glucopyranoside, genipin, β-glucosidase

CLC Number:

Q939.97

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