Optimization of Fermentation Conditions of Surfactin from Bacillus subtilis by Response Surface Methodology

In order to improve the surfactin production capacity of Bacillus subtilis FHYB201030, taking Bacillus subtilis FHYB201030 as the experimental strain, and CPC-BTB (cetylpyridyl chloride-bromothymol blue) value was used as the evaluation index. Single factor tests, Plackett-Burman test, steepest climbing test and response surface test were used to optimize the optimal fermentation conditions for surfactin production. Plackett-Burman test showed that temperature, lactose and glutamic acid (Glu) had significant effects on surfactin yield. The steepest climbing design and the Box-Behnken central combination design three-factor three-level test were used to calculate the culture medium composition with the highest surfactin yield: 25 g/L of lactose, 10 g/L of casein, 3 g/L of beef extract, 10 g/L of peptone, 5 g/L of NaCl, 0.5 mmol/L of Mn²⁺, 2.5 g/L of Glu. The optimum cultivation conditions were temperature of 40 ℃, rotation speed of 200 r/min, filling volume of 30%. Under the fermentation condition, the amount of surfactant produced by Bacillus subtilis FHYB201030 was 0.48 mg/mL, which was 34.56% higher than the 0.35 mg/mL before optimization. This result would lay a good foundation for improving the production level of surfactin.