Statistical optimization of media composition
Determination of suitable variables using Plackett-Burman design
Plackett-Burman design (PDB) was carried out to determine the important variable for CMCase production. Eleven variables, including eight main fermentation medium components and three dummy variables were designed for twelve run experiments [15] and [16]. The nutritional variables are components of the fermentation medium and consist of corn stover, urea, proteose peptone, yeast extract, (NH4)2SO4, KH2PO4, CaCl2·2H2O and MgSO4·7H2O. The factor operating conditions were prepared at two levels, high level (+1) and low level (-1) (Table 1). The dummy variables were used to estimate experimental errors in data analysis. The experimental design for determination of the important variables is presented in Table 2. In this study, the variables with confidence levels above 95% were considered to be significant, affecting CMCase production. All experiments were performed in triplicates and the average of cellulase activity (Unit/ml) was taken as the response.