Statistical Optimization of Alkaline Protease Production by Bacillus cereus FT11 using Response Surface Methodology

Abstract

The alkaline protease activity of soil isolated strain Bacillus cereus FT11 (Accession number: MH571874) was estimated to be 252 U/mL through protease assay under standard cultural conditions. As an important industrial enzyme, alkaline protease production by microbial isolates must be optimized to achieve a costeffective and enhanced production process. Here, the enzyme production was optimised through three variable three level Box-Behnken design. The variables tested include incubation temperature, broth pH and nitrogen substrate concentration. The statistical model comprised of 15 experimental runs and production conditions were optimised with a second-degree statistical model. The optimum conditions resulted in maximum enzyme production were: temperature 36 ⁰C, pH 9.0 and 2.6% substrate concentration. A protease activity of 1610 U/mL was the maximum response predicted from the model. The accuracy of the regression model's predictions was confirmed and the statistical model were validated through repeated experiments conducted under optimized conditions. The values obtained was close to the predicted value (1610 U/mL) and higher than the activity obtained before optimisations, indicating 539% increase in enzyme production following optimization. The results highlight the importance of cultural optimization in enhancing enzyme yield and demonstrate effectiveness of statistical tools in streamlining experimental design.