Response surface optimization of medium composition for alkaline protease production by Bacillus clausii

A culture medium for production of bacterial alkaline protease was developed following preliminary studies by means of response surface method. Central composite design was applied to optimize the medium constituents and explain the combined effects of three medium constituents, viz., sucrose, yeast extract and potassium nitrate. The optimum values for the tested variables were; sucrose 11 g l−1, yeast extract 5 g l−1 and KNO3 5.2 g l−1. A second-order model equation was suggested and then validated experimentally. The model adequacy was very satisfactory as the coefficient of determination was 0.94. The maximum alkaline protease production was 1520 ± 35 U ml−1at 42 h of incubation which showed about 1.5-fold increase in protease production over the central point and an overall 6-fold enhancement (1520–250 U ml−1) over the basal medium.