Purification and Characterization of α-Amylase from Bacillus subtilis Isolated from Local Environment

The present study is aimed at assessing the ability of Bacillus subtilis to convert starch into reducing sugars. Maximum enzyme activity showed by B. subtilis was 228 U/ml. B. subtilis showed optimum growth at pH 7 and optimum temperature for the growth of the bacterial isolate was found to be 37oC. The optimal pH and temperature of the purified amylase were 7.0 and 37oC. The purified enzyme was found to be stable in the pH range of 5.0 to 9.0. The enzyme was stable for 1 h at temperatures ranging from 25-80oC, while at 80oC, 38% of its maximum activity was lost. Maximum α-amylase activity was determined in 1% starch concentration. The purified amylase could be detected as a single band of 59 kDa by SDS polyacrylamide gel electrophoresis. Alpha-amylase activity was improved by treating it with an alkylating agent, N-methyl-N nitro-N-nitroso guanidine. Out of 39 mutants of B. subtilis, m-39 showed 3.16 fold higher activities (721.5 U/ml) than the parent strain. B. subtilis can be exploited for starch conversion biotechnologies.