Statistical optimization of crude oil bio-degradation by a local marine bacterium isolate Pseudomonas sp. sp48

Pseudomonas sp. sp48, a marine bacterium isolated from Bahary area (Alexandria, Egypt), showed a high potency for oil degradation up to 1.5%. Additionally, it showed an ability to consume aromatic hydrocarbons (phenol & naphthalene) and aliphatic (pentadecane) reaching to 79; 73; 62%, respectively. In the current study, Plackett-Burman factorial design was applied to evaluate culture conditions affecting the degradation potency. Analysis of Plackett-Burman design results revealed that, the most significant variables affecting oil removal were magnesium sulfate, inoculum size, glucose and Triton X-100. To optimize the levels of these significant variables Response Surface Methodology (RSM) was followed. In this respect, the three-level Box-Behnken design was employed and a polynomial model was created to correlate the relationship between the three variables and oil removal. The optimal combinations of the major constituents of media that was evaluated from the non-linear optimization algorithm of EXCEL-Solver was as follows: (w/v%) 1 crude oil, 0.5 peptone, 0.5 yeast-extract, 1 ammonium chloride, 0.7418 D-glucose, 0.5 MgSO₄·7H₂O, 0.1 Triton X-100 and inoculums size 4.18 ml% in natural sea water at pH 7; 30 °C incubation temperature, 200 rpm for 6 days. The predicted optimum oil removal was 89%, which is 2.4 times more than the basal medium.