Abstract: Plackett-Burman design was used to evaluate importance of the selected fifteen internal factors to the growth of Getotrichum candidum and Aspergillus oryzae. Results showed that KCl, MgSO4, K2HPO4, NaNO3 and saccharose were the main factors affecting the growth of the multiple strains. In addition, the central composite design and response surface analysis were used to determine the optimal levels of the main factors. The optimized medium was determined as follows: saccharose 32.5 g/L, KCl 2.4 g/L, MgSO4 0.48 g/L, K2HPO4 1.5 g/L, NaNO3 4.0g/L and natural pH. Under these conditions, cell density of multiple strains can increase from 1.35 ×107 CFU/ml to 1.49×108 CFU/ml and time used to obtain maximal cell production decreases from 48 h to 32 h. The experimental data have validated the theoretical values.

Key words: rapeseed meals, reduce toxicity, Plackett-Burman design, response surface methodology