Purification and Some Properties of a Thermostable α-Amylase Produced from Bacillus subtilis Isolated from the Soil

This work reports the isolation, purification and some properties of a thermostable α-amylase producing Bacillus subtilis isolated from the soil. Soil samples were collected and screened for thermophilic bacterial strains with amylase activity and to examine the amylase heat tolerance potentiality. The isolate was Gram positive, motile rod, bearing terminal endospore. The optimum temperature of amylase activity was at 50oC. Maximum enzyme production occurred at pH 7.0. Corn starch produced the best enzyme activity of 1.82 U/mg protein and was found to be the best carbon source followed by soluble starch (1.21 U/mg protein). Among the five nitrogen sources studied, peptone caused the production of highest enzyme activity of 1.79 U/mg protein, followed by casein (1.38 U/mg protein). Ammonium sulphate proved to be the less suitable nitrogen source for enzyme production. Calcium chloride stimulated enzyme production (2.0 U/mg protein) more than other salts. These characteristics of Bacillus subtilis suggests its promising characteristics for various biotechnological applications.Key words: α-amylase; Bacillus subtilis; Thermophile; Enzyme purificatio