Application of Box-Behnken Design for the Optimization of Citric Acid Production from Corn Starch Using Aspergillus niger

Citric acid production from hydrolysed corn starch was optimized in this study. Response surface methodology (RSM) was employed for the analysis of the simultaneous effect of substrate concentration, broth pH and fermentation temperature on the concentration of citric acid produced during fermentation of hydrolysed corn starch. A three-variable, three-level Box-Behnken design (BBD) comprising 15 experimental runs was used to develop a second degree statistical model for the optimisation of the fermentation conditions. The optimal fermentation conditions that resulted in the maximum citric acid concentration were substrate concentration; 50 g/L, broth pH; 2.00 and fermentation temperature; 25ºC. Under these conditions, the concentration of citric acid was obtained to be 31.96 g/L. Validation of the model indicated no difference between predicted and observed values.