Purification and characterization of an extracellular thermostable alkaline α-amylase from the moderately halophilic bacterium, Bacillus persicus

Background: Today a large number of bacterial amylases are available commercially in industry. The goal of the present study was purification and biochemical characterization of an extracellular thermostable alkaline α-amylase from the novel moderately halophilic, Bacillus persicus from the Aran-Bidgol, Iran.   Methods : Purification of enzyme, was carried out by acetone precipitation, ultrafiltration and Q-Sepharose cation exchange chromatography. Results : The purified native enzyme showed a molecular mass of ۵۳ kDa composed of a monomer by SDS–PAGE. The optimum pH, temperature and NaCl concentration were ۱۰, ۴۵ ∘C and ۰.۸۵ M respectively. It retained ۵۰% of activity at ۱.۲۵ M NaCl and about ۷۳% of activity at highly alkaline pH of ۱۰.۵, therefore it was a moderately halophilic and also can activate by divalent metal ions especially Ca۲+ and Mg۲+. The apparent values of Km and Vmax were obtained ۱.۰۵۳ mg/ml and ۳۵۶μ/min respectively. Conclusion : In the present study we report the purification and characterization of a moderately halophilic α-amylase from a newly isolated Bacillus persicus. The purified enzyme shows interesting properties useful for industrial and biotechnological applications. The molecular cloning and structural studies of this α-amylase are in progress in our laboratory.