Purification and characterisation of α-amylase produced by mutant strain of Aspergillus oryzae EMS-18

α-Amylase produced by a mutant strain of Aspergillus oryzae EMS-18 has been purified to homogeneity as judged by sodium dodecyle sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme was purified by using 70% ammonium sulphate precipitation followed by anion exchange chromatography on DEAE-Sephadex column and gel filtration on Sephadex G-100. An enzyme purification factor of 9.5-fold was achieved with a final specific activity of 1987.7 U/mg protein and overall yield of 23.8%. The molecular weight of purified α-amylase was estimated to be 48 kDa by SDS-PAGE. The purified enzyme revealed an optimum assay temperature and pH 40°C and 5.0, respectively. Except Ca⁺⁺ all other metal ions such as Mg, Mn, Na, Zn, Ni, Fe, Cu, Co and Ba were found to be inhibitory to enzyme activity.