Purification and Physicochemical Properties of an Extra Cellular Amylase From a Strain of Bacillus Amyloliquefaciens Isolated From Dry Onion Powder

An extracellular α-amylase from Bacillus amyloliquefaciens, isolated from dry onion powder, has been purified to homogeneity by ammonium sulfate fractionation, adsorption on starch, column chromatography on DEAE-cellulose, and gel filtration on Sephadex G-100 column. The enzyme consisted of one polypeptide chain with a molecular weight of 60,000. The isoelectric point was pH 5.2, the pH optimum 5.5 and the temperature optimum ranging from 50°-70°C. Prolonged digestion by trypsin did not affect the catalytic properties of the enzyme. The Km for starch was 6.9 mg/ml. The enzyme was quite stable at 50°C, but lost about 85% of its activity at 60° after 30 min (pH 6.0).