摘要 : An amylase (est. <i>M</i>_w 150 kDa) was purified 27.39-folds from the culture broth of <i>Bacillus megaterium</i> VUMB109. The purified enzyme was not inhibited by <i>p</i>-chloromercuro benzoate and iodoacetamide (10 m... 展开 An amylase (est. <i>M</i>_w 150 kDa) was purified 27.39-folds from the culture broth of <i>Bacillus megaterium</i> VUMB109. The purified enzyme was not inhibited by <i>p</i>-chloromercuro benzoate and iodoacetamide (10 mM), it rapidly decolorized the blue color of starch-iodine complex and produced alpha -anomeric products from starch hydrolysis, thus, it is an endo-attacking alpha -amylase. The enzymatic activity was not affected by any metal ion and EDTA, therefore, it is not in the class of metalloenzyme. The purified alpha -amylase showed higher affinity (<i>K</i>_m=1.5 micro M; <i>V</i>_max/<i>K</i>_m=0.38 and <i>K</i>_cat/<i>K</i>_m=2.5x10⁶) to starch than other tested substrates like amylose, amylopectin and glycogen. Maltooligomer mixture with high proportion of maltopentaose (G5) and maltotriose (G3) was produced during hydrolysis of starch, amylopectin and amylose. It exhibited high degree of hydrolysis on raw potato starch than wheat, rice and corn starches. Thus the studied alpha -amylase could be exploited as a useful catalyst in the bioprocessing of maltooligomer mixture as food supplement for baby and aged people. 收起