PRODUCTION AND CHARACTERIZATION OF THERMOSTABLE ALPHA AMYLASE BY BACILLUS STEAROTHERMOPHILUS NCIM 2922

Production of thermostable alpha amylase by Bacillus stearothermophilus NCIM 2922 has been investigated using starch as a carbon source. The effects of pH, temperature and concentration of starch on alpha amylase production were examined. The maximum production of alpha amylase was obtained with temperature 50°C, pH 7 and 0.3% (w/v) starch. The growth kinetic study indicates μ max , K s , T d and Y x/s were 0.19/h, 0.78 g/l, 3.64 h and 0.4g cell/g starch, respectively. Optimum activity of partially purified alpha amylase was observed at 80°C and pH 6.5. The kinetic parameters K m and V max , of alpha amylase were 1.7 mg/ml and 112.8 μmole/min, respectively. Irreversible thermal inactivation of the enzyme was studied at different temperatures. The values of inactivation rate constant (K i ) and half life (t 1/2 ) at 80, 90, 100°C were 0.32/h, 0.37/ h, 0.75/h and 129.93 min, 112.37 min, 55.2 min respectively. The activation energy of irreversible thermal inactivation of alpha amylase was found to be 37.57kJ/mol.