2.5.1. Optimal Fermentation Conditions for Biosurfactant Production

To investigate the optimal carbon source for biosurfactant production with P. mosselii MP-6, various carbon sources were added to a minimal salt medium (MSM) at concentrations of 20 g/L glucose, 20 g/L sodium citrate, 20 g/L sodium acetate, 20 g/L sodium oxalate, 2 mL/100 mL of gasoline, and 2 mL/100 mL of rapeseed oil, respectively. The MSM used in this study contained 3.7 g/L KH₂PO₄, 5.2 g/L K₂HPO₄·3H₂O, 2 g/L NH₄Cl, 1 g/L Na₂SO₄, 0.1 g/L MgSO₄, and 1 mL trace metals’ solution (0.3 g/L FeCl₂·4H₂O, 0.038 g/L CoCl₂·6H₂O, 0.02 g/L MnCl₂·4H₂O, 0.014 g/L ZnCl₂, 0.0124 g/L H₃BO₃, 0.04 g/L Na₂MoO₄·2H₂O, 0.0034 g/L CuCl₂·2H₂O). P. mosselii MP-6 was inoculated into different media at a 10% inoculum rate and incubated under 30 °C, 130 rpm. After 72 h, the samples were collected, and the emulsification stability (E24) as well as the surface tension of each sample were measured.

P. mosselii MP-6 was inoculated into the MSM with 20 g/L sodium citrate at a 10% rate and then incubated on a shaker at 30 °C, 130 rpm. Samples were taken at 0, 24, 48, 72, 96, 120, 144, and 168 h for OD₆₀₀ measurements. The cell-free supernatants were also sampled for measurement of their emulsification stability (E24) and surface tension.