Production and properties of alpha-amylase from Bacillus sp. BKL20

As a result of screening Bacillus sp. strains isolated from different natural substrates, strain BKL20 was identified as a producer of a thermostable alkaline alpha-amylase. Maximum production of this alpha-amylase was achieved by optimizing culture conditions. Production of alpha-amylase seemed to be independent of the presence of starch in the culture medium and was stimulated by the presence of peptone (0.3%, m/v) and yeast extract (0.2%, m/v). The enzyme was thermostable and retained amylolytic activity after 30 min of incubation at 60 and 70 degrees C. High activity was maintained over a broad pH range, from 6.0 to 11.0, and the enzyme remained active after alkaline incubation for 24 h. Bacillus sp. BKL20 alpha-amylase was not stimulated by Ca2+ or other bivalent metal cations and was not inhibited by EGTA or EDTA at 1-10 mmol/L, suggesting that this alpha-amylase is a Ca2+-independent enzyme. It also showed good resistance to both oxidizing (H2O2) and denaturating (urea) agents.