alpha-Amylases of B. amyloliquefaciens and a mutant strain were purified through a series of four steps and the purity of enzymes was checked by electrophoresis. Differences were found among the enzymes with respect to pH, temperature, stability, K-m and V-max and binding of Ca. The degradation ability of wild type alpha-amylase on starch granules from various botanical sources (potato, sweet potato, corn, wheat and rice) were examined by scanning electron microscopy and by kinetic assays. Differences in enzyme activity on raw granules were noted. The gene coding mature enzyme was amplified by PCR and expressed in E. coli under trc and T7 promoter. (c) 2004 Published by Elsevier Ltd.