BIOCHEMICAL CHARACTERIZATION OF FREE AND IMMOBILIZED α-AMYLASE FROM ASPERGILLUS NIGER AND ITS BIOTECHNOLOGICAL APPLICATIONS

alpha-amylase is widely used in various biotechnological applications such as food processing, starch, and paper industries, hydrolyzing starch, glycogen, and other polysaccharides into glucose, maltose, and oligosaccharides. Aspergillus niger alpha-amylase was partially purified by ammonium sulphate fractionation with 1.409 fold purity and 54.88% yield. The partially purified alpha-amylase was immobilized on sodium alginate with calcium chloride by ionotropic gelation with glutaraldehyde as a cross-linking agent. Immobilized alpha-amylase exhibited 50% of its original activity. The soluble and immobilized alpha-amylases exhibited maximum activity at pH values 7.5 and 8.0, respectively. The optimum temperature for both the soluble and immobilized enzymes was 35 degrees C. The immobilized enzyme was more pH and thermally stable than the soluble one. The substrate starch was hydrolyzed by soluble (Km 0.6 mg/ml, V-max 16.05 mg/ml/min) and immobilized alpha-amylase (Km 0.65 mg/ml, V-max 17.41 mg/ml/min) with high efficiencies. On the basis of the results obtained, immobilized alpha-amylase could be employed in the saccharification of starch processing.