Production of protease from a new alkalophilic Bacillus sp. I-312 grown on soybean meal: optimization and some properties

An oxidative and SDS-stable alkaline protease having industrial significance and produced by an alkalophilic Bacillus sp. I-312, which was isolated from the heavily polluted tidal mud flat and sea water near Songdo in Inchon, Korean West Sea (Yellow Sea). Maximum activity (42,520 U ml−1) was obtained when the bacterium was grown in a medium containing (g l−1): soybean meal, 15; wheat flour, 10; fructose, 5; K2HPO4, 4; Na2HPO4, 1; CaCl2, 0.05; Na2CO3, 8 at 32 °C for 48 h incubation period with agitation of 250 rpm. The optimum pH and temperature of the enzyme were around 11 and 60 °C, respectively. The alkaline protease also showed extreme stability towards SDS and oxidizing agents, which retained its activity 87.8 and 87.5% activity on treatment with 5% SDS and 5% H2O2 for 72 h, respectively. The alkaline serine protease secreted by Bacillus sp. I-312 is industrially important from the perspectives of its abilities to function in alkaline pH and to show stability in broad pH ranges in addition to its stability towards SDS and hydrogen peroxide, suggesting that it is a potential candidate as an additive in detergent formulations.