Isolation and characterization of a novel oxidant- and surfactant-stable extracellular alkaline protease from Exiguobacterium profundum BK-P23.

The novel protease from Exiguobacterium profundum BK-P23 was partially purified by ammonium sulfate precipitation and further purified Mono Q 5/50 and Superdex 200 10/300 column chromatography. The enzyme was purified 10.23-fold with a yield of 14%. The molecular weight was estimated to be 52 kDa by SDS-PAGE. The enzyme was most active at a pH of 8.0 and temperature of 40°C and the enzyme was stable between a pH of 7 and 10 and up to a temperature of 50°C. The enzyme activity was enhanced by CaCl2 but was slightly inhibited by CoCl2 , MgSO4 , and AgNO3 . In addition, this enzyme was completely inhibited by phenylmethylsulfonyl fluoride, indicating that this enzyme was a serine protease. Furthermore, the alkaline protease was more stable in the presence of surfactants such as Triton X-100, which was followed by Tween 80 and SDS. Moreover, the enzyme was highly stable in the presence of 1% oxidizing agent (H2 O2 ). The enzyme also has significant stability (70%-80%) in a few organic solvents. Thus, the increased stability of the enzyme in the presence of oxidizing agent, surfactants, and organic solvents may find potential applications in the detergent industry and peptide synthesis in nonaqueous media.