optimized production and characterization of a detergentstable 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 plackettburman 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 3100uml was 45 folds higher than those obtained by the use of the initial conditions 680uml additionally a new extracellular 51kdaprotease designated saplf was purified and biochemically characterized from strain c250r it shows optimum activity at 70c and ph 10 its halflife times at 70 and 80c were 10 and 6h 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 25l from bacillus licheniformis this study demonstrated that saplf has a high detergent compatibility and an excellent stain removal compared to alcalase ultra 25l which offers an interesting potential for its application in the laundry detergent industry