Purification and Properties of Thermostable Alkaline Protease from Bacillus subtilis K-30

B. subtilis K-30 isolated from soil sample collected from detergent industry produced alkaline protease. Thermostable extracellular alkaline protease (EC 3.4.21.14), suitable for use in detergents, was purified by ion exchange chromatography from Bacillus subtilis K-30 and its properties were examined. The purified enzyme had a molecular weight of 29kDa as determined by SDS-PAGE. The optimal pH and temperature of the purified enzyme was found to be 10 and 55 degrees C, respectively. It was capable of hydrolyzing many soluble and insoluble protein substrates. Casein was the best substrate among the substrates tested (BSA, egg albumin, gelatin). The enzyme activity was inhibited by Cu2(+), Hg2+ and Zn2+ at 5mM whereas Ca2+, Mg2+, and Mn2+ had stimulatory effect. The protease was 100% inhibited by PMSF, indicating serine protease activity. The enzyme retained more than 40 percent activity after 30 min incubation at 60 degrees C in the presence of detergents such as Henko and Vim ultra, indicating its suitability in detergent industry.