Cloning, expression and characterization of β-glucosidase from Aspergillus fumigatus

Abstract:

Exploring new β-glucosidase genes is of great importance to industrialize β-glucosidase. The genomes of Aspergillus fumigatus contain a bgl gene, which encodes a 65 kDa putative β-glucosidase. The bgl gene was cloned into an expression plasmid and transformed to Escherichia coli BL21 (DE3). The bgl was expressed upon induction of Isopropyl β-D-1-thiogalactopyranoside (IPTG). The recombinant protein was purified by GST-tag affinity chromatography. The purified recombinant Bgl was characterized using Esculin as substrate. The optimum temperature and pH were 45 ℃ and 5.0?6.0, respectively. The Km for Esculin was 17.7 mmol/L. The enzyme was stable in the range of pH 4?7. After incubation at 70 ℃ for 2 h, the recombinant Bgl remained 60% of its activity. Metal ions and chemical reagents had different influences on the activity of β-glucosidase. Ca2+ (1 mmol/L) could increase enzyme activity slightly. On the contrary, the enzyme activity was greatly inhibited by 5 mmol/L Sodium dodecyl sulfate (SDS). Based on our results, the A. fumigatus Bgl was thermostable β-glucosidase.