Production, purification, and characterization of thermostable α‐amylase from thermophilic Geobacillus stearothermophilus

The α‐amylase (α‐1‐4‐D‐glucan glucanohydrolase; EC 3.2.1.1) secreted by Geobacillus stearotermophilus was purified and characterized. Maximum enzyme production was achieved after 24 h cultivation at pH 7.0 and 55°C. The enzyme was active in a broad temperature range, between 50 and 80°C, with an optimum at 70°C; and maximum activity was at pH 7.0. The enzyme was purified using 80% ammonium sulfate precipitation, dialysis, Sephadex G‐100 gel filtration, and DEAE‐cellulose column chromatography, with a 46‐fold and 65% recovery and showed a MW of 63 kDa by SDS‐PAGE. It was determined that the purified enzyme was stable at 50 and 60°C, and pH 7.0. It was determined that the purified enzyme was stable at 50 and 60°C at the end of 2 h. The enzyme retained 100% activity pH 7.0 at the end of 3 h. The enzyme was activated by Ca2+, Mn2+, and Triton X‐100, but strongly inhibited by Cu2+, Zn2+, Fe2+, and Hg2+. The enzyme follows Michaelis–Menten kinetics with Km and Vmax values of 0.051 mM and 1.424 μmol/min, respectively.