ABSTRACT
Alpha-amylase production by Bacillus subtilis was studied under different cultivation conditions. The maximum alpha-amylase production occurred after an incubation period of 48 h, temperature 40 degrees C and pH 7.5. Among the defined carbohydrates, starch (1%) was the best carbon source. The organism grew better and produced high levels of alpha-amylase using peptone as nitrogen source. The produced alpha-amylase was immobilized on various carriers by different methods and the properties of the enzyme were compared before and after immobilization. The optimum pH of the immobilized enzyme was changed to acidic range. The optimum reaction temperature of immobilized enzyme was shifted slightly to 70-80 degrees C. Both of Km values and Vmax and thermal stability of immobilized enzyme were found to be higher than that of free one. Among the tested metals CaCl2 exerted a stimulating effect on the activity of alpha-amylase.
