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α-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, Km and Vmax and binding of Ca. The degradation ability of wild type α-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.

The degradation abilities of α-amylase from Bacillus amyloliquefaciens and β-amylases from Bacillus cereus and soybean on raw starch granules from various botanical sources (potato, sweet potato, wheat, rice and corn) were examined by scanning electron microscopy. All the amylases showed different degradation patterns on starch granules. The α-amylase was more efficient than the β-amylases. α-Amylase showed both centrifugal and centripetal hydrolysis on corn, rice and wheat granules, but only centrifugal hydrolysis on potato granules. On the other hand, β-amylase moved very slowly on granules. The kinetic assays which explain the release of maltose were carried out at 12, 18 and 24 h. The rice granules were found to be the best substrate for enzymic hydrolysis by α and β-amylases. In addition, While Bacillus cereus β-amylase hydrolyzed corn granules efficiently at 45°C; soybean β-amylase was 60% less active than bacterial β-amylase at the same temperature.