A novel detergent additive: Organic solvent- and thermo-alkaline-stable recombinant subtilisin

In the present work, subtilisin gene from Bacillus subtilis PTTC 1023 was synthesized, cloned into the vector pD441-NH and expressed in E. coli BL21 (DE3). Recombinant subtilisin was purified in a single-step procedure by affinity chromatography. The molecular mass of the purified protein was determined to be about 40 kDa by SDS-PAGE. The optimum pH and temperature values of its proteolytic activity were 10.5 and 50 °C, respectively and retained more than 70% and 89% of its activity in pH range of 7-12 and 30-60 °C, respectively. Enzyme purity was estimated to be about 200- fold greater than that of the crude extract and subtilisin had a specific activity of 56.16 U/mg, with a yield of about 87.9%. It was completely inhibited by phenylmethanesulfonyl fluoride, which strongly suggests its belonging to serine protease family. Interestingly, subtilisin protease displayed a significant compatibility with commercial detergents, and tolerance organic solvents, metallic ions and surfactants. The findings obtained demonstrated that protease of B. subtilis could potentially be used in future applications as an additive in detergent formulations.