Characterization and biodegradation of motor oil by indigenous Pseudomonas aeruginosa and optimizing medium constituents

An indigenous Gram-negative bacterium (identified as Pseudomonas aeruginosa SU-1) isolated from the oily sludge of a storage tank was applied to motor oil degradation. Residual motor oil content was measured by gas chromatography (GC) during a 24 d cultivation period. Experimental results revealed that P. aeruginosa SU-1 possessed strong biodegradation ability. This strain tended to bioflocculate, and the surface tension of broth decreased by producing an unknown emulsifying agent. Biodegradation was accelerated from 55.9% to 64.4% by adding yeast extract. Statistical experimental design was used to optimize the medium constituents for motor oil biodegradation by P. aeruginosa SU-1 in shake flasks. Experimental results showed that the optimal medium constituents were motor oil 14,401 ppm, K2HPO4 4.049 gL−1, and basis medium including (NH4)2SO4 1 gL−1, MgSO4·7H2O 0.5 gL−1, NaCl 1 gL−1, trace element 2 mL L−1, and yeast extract 1 gL−1. The predicted maximal amount of motor oil for biodegradation was 5028.81 ppm, and the experimental value was 5095.7 ppm. The biodegradation capacity of this strain was consequently enhanced by 1.9-fold from 2680 to 5095 ppm for 15 d of culture.