Optimized production and characterization of a detergent-stable protease from Lysinibacillus fusiformis C250R

In this study, we aimed to optimize the cultural and nutritional conditions for protease production by Lysinibacillus fusiformis strain C250R in submerged fermentation process using statistical methodology. The most significant factors (gruel, wheat bran, yeast extract, and FeSO4) were identified by Plackett-Burman design. Response surface methodology (RSM) was used to determine the optimum levels of the screened factors and their interaction. Under the optimized conditions, protease yield 3100 U/mL was 4.5 folds higher than those obtained by the use of the initial conditions (680 U/mL). Additionally, a new extracellular 51 kDa-protease, designated SAPLF, was purified and biochemically characterized from strain C250R. It shows optimum activity at 70 °C and pH 10. Its half-life times at 70 and 80 °C were 10 and 6-h, respectively. Irreversible inhibition of enzyme activity of SAPLF with serine protease inhibitors demonstrated that it belongs to the serine protease family. Interestingly, its catalytic efficiency was higher than that of SPVP from Aeribacillus pallidus strain VP3 and Alcalase Ultra 2.5 L from Bacillus licheniformis. This study demonstrated that SAPLF has a high detergent compatibility and an excellent stain removal compared to Alcalase Ultra 2.5 L; which offers an interesting potential for its application in the laundry detergent industry.