Purification and properties of an endoglucanase from Aspergillus niger VTCC-F021


Abstract: An extracellular endoglucanase (EG) from Aspergillus niger VTCC-F021 was purified 2.09-fold to homogeneity with a yield of 18.4%. The enzyme had a molecular mass of 31 kDa and a specific activity of 14.122 U/mg protein. Optimum temperature was observed at 55 °C and optimum pH at 5. The enzyme was stable up to 50 °C and from pH 5 to 6 with residual activity >80% and 60%, respectively. The kinetic constants K_m and V_{max} determined for EG, with carboxyl methyl cellulose as a substrate, were 8.5815 mg CMC/mL and 20.121 U/mg protein, respectively. EDTA increased EG activity by 35% at 5 mM and decreased activity by 12% at 15 mM. The metal ions Cu^{2+} and Fe^{2+} activated EG activity 112%-152% at 5-15 mM. EG showed a high resistance to Tween 20 and Tween 80 at 0.5%-2.0% (w/v) and to ethanol and methanol at 10%-20% (v/v) with a residual activity of >80%. The biochemical properties of EG demonstrated that this enzyme was quite different from those of A. niger strains. These results suggested that EG from A. niger VTCC-F021 could be used to investigate the efficacy of feed enzymes.

Keywords: Aspergillus niger VTCC-F021, carboxymethyl cellulose, endoglucanase, purification, characterization

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