Culture Condition of Pseudomonas aeruginosa F722 for Biosurfactant Production

Pseudomonas aeruginosa F722 produces a biosurfactant (BS) during its degradation of carbon and hydrocarbon compounds. The culture conditions for upgrading the biosurfactant productivity were investigated. The concentration of the biosurfactant produced by P. aeruginosa F722 was 0.78 g/L in C-medium; however, this increased to 1.66 g/L in BS medium, which was experimentally adjusted to optimal conditions. $NaNO_{2}$ was found to be most effective for microbial growth, with an $O.D_{600nm}$ of 1.18 for 0.1 % $NaNO_{2}$. Microbial growths, according to the $O.D_{600nm}$ were 2.53, 2.68, 2.89, and 2.87 for glucose, glycerol, $n-C_{10},\;and\;n-C_{22}$, respectively. Clear zone diameters (cm), indicating biosurfactant activity, were 9.0, 8.8, 5.7, and 8.5 for glucose, glycerol, $n-C_{10},\;and\;n-C_{22}$, respectively. Microbial growth was not consistent with the biosurfactant activity. The best biosurfactant activity was found with a C/N ratio of 20. Under optimal culture condition, the average surface tension decreased from 70 to 30 mN/m after 5 days. With aeration of 1.0 vvm, the biosurfactant produced increased to 1.94 g/L (up to 20%) compared to that of 1.66 g/L with no aeration. With aeration, the velocities of glucose degradation during both the log and stationary growth phases increased from 0.25 and $0.18\;h^{-1}$ to 0.33 and $0.29\;h^{-1}$, respectively, and the time for the culture to arrive at the maximum clear zone diameter became shorter, from 80 down to 60 h with no aeration.