PURIFICATION AND PHYSICOCHEMICAL PROPERTIES OF AN EXTRACELLULAR 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). Copyright © 1979, Wiley Blackwell. All rights reserved