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

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 Km and Vmax 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 Cu2+ and Fe2+ 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.