Biochemical characterization of raw-starch-digesting alpha amylase purified from Bacillus amyloliquefaciens

Alpha amylase (E.C. 3.2.1.1) of Bacillus amyloliquefaciens produced by submerged fermentation was purified to near homogeneity by ion exchange chromatography. Through the process 38.6-fold increase in purity with a specific activity of 72 U/mg proteins was obtained. The apparent molecular weight of the purified enzyme was found to be 58 kDa by SDS-PAGE. The enzyme was relatively stable between pH 5.0-8.0 and temperature between 50 and 60 degrees C. The enzyme did not show any obligate requirement of metal ions but Ca2+ and Cu2+ enhanced the enzyme activity marginally and the thermostability was enhanced in the presence of Ca2+ ions. The purified enzyme exhibited maximal substrate specificity for amylose and efficiency in digesting various raw starches. The K(m) and V(max) of the enzyme was determined using both amylose and soluble starch as substrate. The analysis of the hydrolyzed products of soluble starch by thin layer chromatography showed the yield of maltosaccharides after 6 h of hydrolysis.