Characterization of a Thermotolerant α-amylase Producing Natural Variant of Bacillus Species

Thermotolerant α-amylases have had extensive commercial applications in starch processing, brewing and sugar production, and have almost completely replaced chemical hydrolysis of starch in the starch processing industry. The aim of this study was to determine the characterization of thermotolerant α-amylase producing natural variant of bacillus species In this laboratory study, the isolated bacillus species known as Bacillus licheniformis Shahed-07 was identified by biochemical methods. The bacillus was cultured in liquid media to produce α-amylase. The enzyme production media were assessed controled and optimized for enzyme productivity using various carbon and nitrogen sources. The stability of the enzyme against temperature, pH, metal ions and chelating agents was then determined. Maximum enzyme production was achieved after 26 h cultivation at pH 7.0 and 50°C. Supplementation of medium with 0.5% Tryptophan enhanced the enzyme productivity to 202%, whereas Peptone and Lysin at 0.5% level showed a strong repression. In comparison with the crude α-amylase, the partially purified enzyme had 3.77 fold purity with 32.64 fold increased activity. This enzyme showed amylolytic activity with a single band of 6000 daltons on electrophoresis gel with 0.2% starch. The optimum activity was at pH 7.5 and 70°C. The crude enzyme was stable for 24 h at pH range of 6-7 at 70°C. Hg2+ was completely inhibitory to the enzyme activity, and Mn2+, Fe2+, Co2+ and Ca2+ increased the enzyme activity. The B. licheniformis Shahed-07 strain produced high levels of thermotolerant α-amylase with characteristics suitable for application in starch processing and other food industries. The production process can be commercialized after further optimization for enhancing enzyme production.