Abstract: The crude tannase from Aspergillus niger N5-5 was purified by hollow fiber membrane ultrafiltration and Sephadex G-150 gel chromatography. The properties of the purified tannase were then determined. The results showed that the tannase from Aspergillus niger N5-5 could be purified about 20 folds with a 23.30% recovery. The enzyme was a 64.2 kD protein with a single peptide chain by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The optimal temperature for the enzyme was 45 ℃, and it had good thermostability in the range of 25–45 ℃; the optimal pH value was 5.0, and the enzyme displayed good pH stability in the pH range of 5.0–5.5. In addition, the results of reaction kinetics showed that the Km and vmax values towards the substrate propyl gallate were 0.916 mmol/L and 0.877 mmol/(L·min), respectively.

Key words: tannase, Aspergillus niger, purification, purified enzyme, characterization