Abstract
The biosurfactant produced by Pseudomonas balearica isolated from oil-contaminated sea water was studied in the present research. A range of different growth conditions, such as temperature, pH, incubation period, inoculum size and different carbon/nitrogen sources and different C/N ratios were investigated to determine the optimum conditions for maximum production of a biosurfactant by the selected bacterial strain using a mineral salt medium. The best carbon andnitrogen sources were olive oil and urea, giving biosurfactant yields of 6.23 +/- 0.06 and 6.33 +/- 0.10 mg/ml, respectively. The maximum rhamnolipid production was 6.40 +/- 0.14 mg/ml at C/N (olive oil/ urea) of 30. The highest biosurfactant yield was at pH 7 (6.37 +/- 0.06 mg/ml), with inoculum size 2% (6.29 +/- 0.16 mg/ml), and incubation temperature 30 degrees C (6.18 +/- 0.14 mg/ml) and after a 312 hrs incubation period (6.30 +/- 0.09). The previous investigated nutritional and environmental factors showed the highest emulsification activity. The produced rhamnolipid biosurfactant reduced the surface tension of water from 72 to 34 mN/m. In conclusion, the findings herein demonstrated that the rhamnolipid biosurfactant production by P. balearica can be used during oil hydrolysis.