Optimization of Fermentation Conditions and Media of Bacillus subtilis DZ1

The flaskshaking fermentation conditions and media of Bacillus subtilis DZ1 was studied through the single factor experiments and orthogonal experiments. The results showed that the culture time, fermentation conditions and media had significant effects on the survival of Bacillus subtilis DZ1. The optimal seed age was 12 hours after Bacillus subtilis inoculation, and the best carbon sources and nitrogen sources were soluble starch and yeast extract, respectively. Yeast extract was the most important factor affecting Bacillus subtilis populations, and what was followed was soluble starch. However, K2HPO4 and MgSO4.7H2O had little effects on its populations. The optimum culture media for the strain Bacillus subtilis DZ1 were determined as the mixture of 1% soluble starch, 1% yeast extract, 0.15% K2HPO4, 0.02% MgSO4.7H2O, and 0.01% CaCl2. Under this optimized conditions, the maximum amount of Bacillus subtilis DZ1 reached 44.1 × 10 8 CFU/mL. The single factor experiment results showed that the fermentation conditions were identified as the culture temperature of the shaking table 34 ℃, the initial pH of the medium 7.0, the rotation speed 180 r/min, as well as the inoculation amount 7%.