Enterobacter cloacae MSA4, A New Strain Isolated from the Rhizosphere of a Desert Plant, Produced Potent Biosurfactant Used for Enhancing the Biodegradation of Polycyclic Aromatic Hydrocarbons (PAHs) During the Bioremediation of Spent Motor Oil-Polluted S

Ten bacterial strains were isolated from the rhizosphere of a desert plant and screened for the production of biosurfactant using three screening tests. One of the isolated strains (MSA4) was able to produce a potent biosurfactant, it was selected and identified by the 16S rRNA sequence determination and phylogenic analysis as Enterobacter cloacae MSA4. The crude biosurfactant produced by strain MSA4 was characterized by higher E24 values against crude oil (82.0 2.8 %) and spent motor oil (96.0 2.1 %). Accordingly, it was used for enhancing the biodegradation of PAHs during the bioremediation of spent motor oil-polluted sandy soil. Results of the HPLC analysis show that the potent carcinogenic PAH benzo (a) pyrene was of higher concentrations in the spent motor oil (112.1 1.4 mg/kg soil), followed by the two carcinogenic PAHs, benzo (b) flouranthene (110.2 2.5 mg/kg soil) and flouranthene (82.4 1.7 mg/kg soil). When the crude biosurfactant was applied to the spent motor oil-polluted soil, 98.5 % of the US EPA 14 priority PAHs was degraded. On the addition of NP fertilizer alone no increase of the biodegradation above 89.5 % was recorded, while the addition of BRNP, the biodegradation increased from 89.5 % to reach 98.2 %. This result indicates that the promising factor for enhancing the biodegradation of PAHs is the presence of BR. The present results show that the application of BR alone or in combination with NP fertilizer highly stimulated the native microorganisms in the polluted soil to highly or completely degrade different PAH individuals of the spent motor oil. The use of BR in combination with NP will reduce the actual amount of fertilizers needed for the biodegradation process. On the other hand the use of BR alone promoted the biodegradation of PAHs without using fertilizers, this will reduce the cost of the bioremediation process.