Abstract: Biosurfactants have many applications in petroleum oil industry: they are used for oil storage tank cleaning, for reducing the viscosity of heavy oil, thereby facilitating recovery, transportation and pipelining. Also, they are used for microbial enhanced oil recovery either from residual oil in reservoirs or from oily wastewater. The present study is an investigation of biodegradation of petroleum oil effluents using Pseudomonas aeruginosa ATCC 9027 for producing rhamnolipid biosurfactants. The processes were performed in a mechanically agitated, fully baffled air- sparged 10L glass fermenter with a 5L working volume. The effect of oil concentration (1, 1.5, 2, and 2.5%) on the efficiency of oil biodegradation, rhamnolipid production, surface tension and bacterial biomass were studied. The fermentation with 1.5% oil concentration gave the highest biodegradation for aliphatic hydrocarbons (98.85%), followed by 2% oil concentration (95% degradation), then with 2.5% oil concentration 80% degradation), and finally with 1% oil concentration (66.8% degradation). Also, the complete biodegradation of poly-aromatic hydrocarbons was achieved for all tested oil concentrations. On the other hand maximum rhamnolipid production of 2.7 g/L as rhamnose equivalent and lower surface tension (30.2mN/m) were achieved at 2% oil concentration.