الفهرس 
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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 as residual oil in reservoirs or as oily wastewater.
In the present study the biodegradation of petroleum oil effluents using Pseudomonas aeruginosa ATCC 9027, which produce rhamnolipid biosurfactants, was investigated. The processes were performed in mechanically agitated, fully baffled air-sparged 10L glass fermenter with 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 gave the highest percentage biodegradation for aliphatic hydrocarbons (98.85%), followed by 2% oil (95%), then by 2.5% oil (80%), and finally by 1% oil (66.8%). The results showed that complete biodegradation of poly-aromatic hydrocarbons was achieved for tested oil concentrations.
On the other hand, maximum rhamnolipid production of 2.7 g/L as rhamnose equivalent and lower surface tension (30.2 mN/m) were achieved at 2% oil. The effect of glycerol addition as inducer on the oil biodegradation was also studied. The statistical analysis of the experimental data, using the response surface methodology and central composite design, were applied to optimize the oil biodegradation parameters for the object of increasing the biodegradation rate.
This study showed that the optimum values are: 240 hr for reaction time, 1.5% crude oil and 10% glycerol addition.