Analysis of surfactant production by Bacillus cereus GX7 and optimization of fermentation conditions

Although biosurfactants have many advantages compared to chemical surfactants, biosurfactants are still limited by problems such as low yields and high production costs. In the present study, a strain of Bacillus Cereus (GX7) isolated from an oil tank bottom sludge of Shengli Oil Field (China) was selected as a highly effective surfactant producer. The biosurfactant produced by GX7 was extracted, purified, and analyzed by TLC, FT-IR, and LC-MS/ MS. The results showed that the biosurfactant was surfactin of lipopeptide surfactant. Single-factor experiments were used to optimize the fermentation process of the strain from two aspects: the composition of the fermentation medium (carbon source, nitrogen source) and the fermentation conditions (temperature, pH, inoculation amount, rotation speed, and fermentation time). The surface tension and emulsification index of the fermentation broth were used to evaluate the optimal fermentation conditions. The results showed that the best carbon and nitrogen sources were glucose and peptone, and the optimum temperature, inoculum amount, pH, rotation speed, and fermentation time were 30 celcius, 1%, 7.5, 150 rpm, and 48 h, respectively. After optimization, the surface tension and emulsification index of fermentation broth were 26.84 mN/m and 57.84%, respectively. Moreover, the results also prove that the biosurfactant produced by this strain has good stability in a wide range of temperature, pH, and salt concentration.

Automated summary

In this study, a highly effective surfactant producer strain, Bacillus Cereus GX7, was isolated from the oil tank bottom sludge of Shengli Oil Field in China. The biosurfactant produced by GX7 was identified as surfactin, a lipopeptide surfactant, through TLC, FT-IR, and LC-MS/MS analysis. The fermentation process of GX7 was optimized using single-factor experiments, focusing on the composition of fermentation medium and fermentation conditions. Glucose and peptone were found to be the best carbon and nitrogen sources, and the optimum temperature, inoculum amount, pH, rotation speed, and fermentation time for the strain were determined to be 30°C, 1%, 7.5, 150 rpm, and 48 h, respectively. After optimization, the surface tension and emulsification index of the fermentation broth were 26.84 mN/m and 57.84%, respectively. Furthermore, the biosurfactant produced by GX7 demonstrated good stability over a wide range of temperature, pH, and salt concentration.