Enhanced biomass production study on probiotic Bacillus subtilis SK09 by medium optimization using response surface methodology

The culture conditions of lactose fermenting, spore forming probiotic Bacillus subtilis SK09 isolated from dairy effluent were optimized by response surface methodology to maximize the biomass production. The student’s t-test of the Placket-Burman screening design revealed that the effects of pH, ammonium citrate and peptone were more significant and these variables were further optimized using central composite design. The various effects of the variables were studied using Fisher’s F-test for analysis of variance and a second order polynomial model was developed which fitted well with high statistical reliability and significance. The optimal value of significant variables was found to be pH (6.72), ammonium citrate (0.164%) and peptone (0.85%). At these optimized conditions, the maximum biomass yield was estimated to be 10.051*10 9 CFU/ml. By employing this statistical design, enhanced yield of probiotic biomass B. subtilis SK09 was achieved using cost-effective medium.