Background: Surfactant is one of the most important raw materials used in various industrial fields, such as emulsifiers, corrosion inhibitors, foaming agent and detergent products. However, the commercial surfactant production is still costly and its demand is steadily increasing. This study aims to evaluate the performance of typical strains of Bacillus sp. to produce biosurfactants through a fermentation process. It also included the investigation of effect of initial glucose concentration and the ratio of carbon to nitrogen.

Results: The biosurfactant was produced in the range of 1-2.46 g/L at initial glucose concentrations of 10-70 g/L. The optimum condition was achieved at a carbon to nitrogen ratio of 12.4 with the decrease in surface tension up to 27 mN/m.

Conclusions: For further development and industrial applications, the modified Gompertz equation was proposed to predict the cell mass and biosurfactant production as the goodness of fitting was obtained. The modified Gompertz equation was also extended to enable the excellent prediction of the surface tension.