Otimização de um meio de cultura para a produção de proteases por um Bacillus sp. termofílico

Abstract

Bacillus sp. SMIA-2 grew and produced proteases when cultivated in liquid cultures containing trisodium citrate as a carbon source and ammonium nitrate as a nitrogen source. The maximum activity of the enzyme was reached after incubating the microorganism for 9 hours, with levels of 7.2 U.mg-1 protein. The supplementation of the medium with 2.0 mM of CaCl2 did not improve the activity of the protease, but increased its stability from 2 to 4 hours. The reduction in the amount of inorganic phosphate in the medium from 11.0 to 5.0 mM resulted in an improvement of 82% (13 U.mg-1 protein) in the protease activity. Replacing ammonium nitrate in the medium by 0.1% milk whey increased the protease activity to 25 U.mg-1 protein. In these conditions, the time required for the enzyme to reach a maximum activity increased from 9 to 16 hours. Replacing citrate trissodium in the medium by corn steep liquor (0.5%) not only produced much better enzyme activity, but also delayed the deactivation process which is typical for the production of proteases. The maximum activity reached when these wastes were used in the medium was 59.5 U.mg-1 protein. In addition, the enzyme maintained stable for more than 20 hours, which is favorable for its production on a large scale.