Kinetic study and modeling of biosurfactant production using Bacillus   sp.

Background: Surfactants are one of the most important raw materials used in various industrial fields as emulsifiers, corrosion inhibitors, foaming agents, detergent products, and so on. However, commercial surfactant production is costly, and its demand is steadily increasing. This study aimed to evaluate the performance of typical strains of Bacillus sp. to produce biosurfactants through fermentation. It also included the investigation of the effect of initial glucose concentration and the carbon to nitrogen ratio.
Results: The biosurfactant yield was in the range of 1–2.46 g/L at initial glucose concentrations of 10–70 g/L. The optimum fermentation condition was achieved at a carbon to nitrogen ratio of 12.4, with a decrease in surface tension of up to 27 mN/m.
Conclusions: For further development and industrial applications, the modified Gompertz equation is proposed to predict the cell mass and biosurfactant production as a goodness of fit was obtained with this model. The modified Gompertz equation was also extended to enable the excellent prediction of the surface tension.

Keywords
Bacillus subtilis; Biological surfactants; Biosurfactant production; C/N ratio; Corrosion inhibitors; Emulsifiers; Foaming agent; Glucose; Kinetic modeling; Oil recovery; Surface tension reduction