Statistical Optimization of Process Parameters for Bioplastic (PHA) Production by Bacillus subtilis NCDC0671 Using Orange Peel-Based Medium

Systematic and sequential optimization strategy based on statistical methodology involving one factor at a time approach was used to enhance PHA production by Bacillus subtilis NCDC0671 using orange peel hydrolysate-based medium in shake flask cultures. Medium components exerting a significant influence in PHA production were screened out using the Plackett–Burman design. Following Box–Behnken method, three significant factors influencing PHA production were identified as beef extract, sodium chloride and incubation period. The optimum concentration and interaction effect of these three components were determined by RSM based on Box–Behnken design. The model developed was validated, and the optimum medium containing 2.23 (g/L) beef extract, 0.72 (g/L) sodium chloride and 48 h of incubation period led to maximum PHA production of 5.09 g/L, which was 2.49-fold higher than the unoptimized medium. The ANOVA results established the significance of the model ( p