Comparison of degradation abilities of α- and β-amylases on raw starch granules

The degradation abilities of alpha-amylase from Bacillus amyloliquefaciens and beta-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 alpha-amylase was more efficient than the beta-amylases, alpha-Amylase showed both centrifugal and centripetal hydrolysis on corn, rice and wheat granules, but only centrifugal hydrolysis on potato granules. On the other hand, beta-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 alpha and beta-amylases. In addition, While Bacillus cereus beta-amylase hydrolyzed corn granules efficiently at 45 degrees C; soybean beta-amylase was 60% less active than bacterial beta-amylase at the same temperature. (C) 2000 Elsevier Science Ltd. All rights reserved.