Article

In the present study, an indigenous biosurfactant-producing bacterium, Rhodococcus sp. BAP-1, with effective fluoranthene-degrading ability was isolated from crude-oil contaminated soil. The biodegradation data indicated that Rhodococcus sp. BAP-1 grew well in the presence of 20 mg·L^-1 of fluoranthene, whereas in the presence of 150 mg·L^-1 of fluoranthene, the biodegradation rate almost remained at low levels. During growth on mineral salts medium, the bacterium could produce biosurfactants. As a result of biosurfactant synthesis, the surface tension of the culture broth was reduced, thus facilitating the contact between the bacterium and hydrocarbon. According to the experimental results, emulsification was probably not the leading mechanism that occurred simultaneously during the biodegradation process. Pollutants might be growing as a confluent biofilm and the uptake system might have a high specific affinity; an interfacial uptake mechanism may play a predominant role in the biodegradation process. Fourier transform infrared spectroscopy showed that the biosurfactant contained aliphatic hydrocarbons. A disruption of the cell surface in certain zones was observed by scanning electron microscopy in some of the cells grown in the presence of 150 mg·L^-1 of fluoranthene, which indicated that drastic changes of the cell surface morphology might occur under different growth conditions. The results of this study collectively suggest that Rhodococcus sp. BAP-1 may be useful in the bioremediation of environments contaminated with polycyclic aromatic hydrocarbons.