Thermostable alpha-amylase production using Bacillus licheniformis NRRL B14368

Maximum amount of extracellular alpha-amylase of B. licheniformis NRRL B14368 was obtained at the stationary phase. Highest yield of alpha-amylase was achieved with high level of crude protein and low carbohydrate level. There was a catabolite repression in the organism. Protease was produced concurrently with alpha-amylase. It was also observed that soyabean acts as an inhibitor of the protease. Optimum pH and temperature of alpha-amylase were 5-7 and 76 degrees C respectively. It was also observed that alpha-amylase production was a non-growth associated product. Maltose was an excellent inducer for alpha-amylase production. Ca2+ (0.01 M) increased the thermostability of the enzyme. Alpha-amylase purification studies were carried out by using isopropanol, acetone, ammonium sulphate solution, ion exchange chromatography. Acetone was found most suitable for the separation of alpha-amylase. Protein recovery and relative enzyme activity (as compared to that of the maximum activity of the crude enzyme) were 30.77% and 3.03 respectively.