Purification and Characterization of Extracellular alpha-amylase from Aspergillus niger K8

ASPERGILLUS NIGER K8 was selected from twenty-two fungal isolates for alpha-Amylase production. The crude enzyme was partially purified and precipitated by salting out with ammonium sulphate. The fraction salted out with 60% ammonium sulphate saturation showed the highest specific alpha-amylase activity with 5.42 folds of purification than that of free extract. The optimum temperature for alpha-amylase enzyme activity was at 60 degrees C. The enzyme was very stable at 60 degrees C for 1 hr and retained more than 80% of its original activity. The optimum specific activity for A. niger K8 was in a narrow range of pH 5.0-6.0. Alpha amylase enzyme was stable at all pH tested. However, it retains more than 75% of its original activity for 1 h at pH value 5.5.