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Abstract

α-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 α-amylase was partially purified by ammonium sulphate fractionation with 1.409 fold purity and 54.88% yield. The partially purified α-amylase was immobilized on sodium alginate with calcium chloride by ionotropic gelation with glutaraldehyde as a cross-linking agent. Immobilized α-amylase exhibited 50% of its original activity. The soluble and immobilized α-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 ºC. 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 αamylase (Km 0.65 mg/ml, V max 17.41 mg/ml/min) with high efficiencies. On the basis of the results obtained, immobilized α-amylase could be employed in the saccharification of starch processing. INTRODUCTION: Alpha-amylases (E.C.3.2.1.1) are enzymes that catalyze the hydrolysis of internal α-1,4-glycosidic linkages in starch into low molecular weight products, such as glucose, maltose, and maltotriose units. Amylases are among the most important enzymes and are of great significance for biotechnology, constituting a class of industrial enzymes having approximately 25% of the world enzyme market 1, 2. The Aspergillus species produce a large variety of extracellular enzymes, and amylases are the ones with the most significant industrial importance. Filamentous fungi, such as Aspergillus oryzae and Aspergillus niger, produce considerable quantities of enzymes that are used extensively in the industry.