Salt-independent thermophilic α-amylase from Bacillus megaterium VUMB109: An efficacy testing for preparation of maltooligosaccharides

Abstract

An amylase (est. Mw 150kDa) was purified 27.39-folds from the culture broth of Bacillus megaterium VUMB109. The purified enzyme was not inhibited by p-chloromercuro benzoate and iodoacetamide (10mM), it rapidly decolorized the blue color of starch–iodine complex and produced α-anomeric products from starch hydrolysis, thus, it is an endo-attacking α-amylase. The enzymatic activity was not affected by any metal ion and EDTA, therefore, it is not in the class of metalloenzyme. The purified α-amylase showed higher affinity (Km=1.5μM; Vmax/Km=0.38 and Kcat/Km=2.5×106) 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 α-amylase could be exploited as a useful catalyst in the bioprocessing of maltooligomer mixture as food supplement for baby and aged people.