Purification and characterization of a thermostable alpha-amylase from Bacillus stearothermophilus

A soil isolate of Bacillus stearothermophilus was found to synthesize therm ostable alpha -amylase. The enzyme was purified ro homogeneity by ammonium sulfate fractionation and IECC on DEAE-cellulose column The purified enzyme was considered to be a monomeric protein with a molar mass of 64 kDa. as d etermined by; SDS-PAGE. The enzyme showed a wide range of pH tolerance and maximum activity at pH 7.0. The temperature tolerance was up to 100 degrees C with more than 90 % catalytic activity; the maximum activity was observed at 50 degreesC, Divalent metal ions exhibited inhibitory effect on the enz yme activity. However, proteinase inhibitor did not react positively.