Biosurfactant Produced By Rhodococcus Erythropolis And Its Effect In The Bioremendiation Of Oil-contaminated Soil

Oil pollution is an environmental problem of increasing importance. Hydrocarbon-degrading microorganisms, adapted to grow and thrive in oil-containing environments, have an important role in the biological treatment of this pollution. One of the limiting factors in this process is the bioavailability of many fractions of the oil. The hydrocarbon-degrading microorganisms produce biosurfactants of diverse chemical nature and molecular size. The activity of bacterial biosurfactants in bioremediation stems from their ability to increase the solubility of hydrophobic water-insoluble substrates as well as the insoluble surface of the cells. So that the solubility and bioavailability of hydrocarbons are improved. In either case, they can stimulate the growth of oil-degrading bacteria and improve their ability to utilize hydrocarbons. It plays a very important role that determining the characters and effects of different types of the biosurfactants, optimizing the productive conditions in promoting the bioremediation of oil-contaminated environment. In this paper, the type, stability and superior productive conditions of the biosurfactant which was produced by one of the isolated bacteria, Rhodococcus erythropolis,from momoge wetland were determined. The biosurfactant was also used in the simulant experiment about the biodegradation of oil-contamination soil collected from momoge wetland to prove its oil-degrading capability. Main results are as follows:1. This biosurfactant produced by Rhodococcus erythropolis was glycolipid. The activity of the biosurfactant was enhanced optimally at pH of 8.0, NaCl concentration below 1% and temperature of 40℃.2. The optimal condition to produce biosurfactant for Rhodococcus erythropolis is as follow:diesel oil, 15mg/L H₂O₂, 2864mg/L N, 40mg/L FeSO₄·7H₂O. In optimal conditions, the biosurfactant concengtration can reach 2.1g/L.3. Appending the biosurfactant into the oil-contaminated soil can stimuliate the biodegradation. Degradation rate increases 11.78% than control for single strain(Rhodococcus erythropolis 5#), while 6.25% for mixed sample. The half life of the petroleum degradation decreased 8d,6d,respectively.4. The optimum additional concentration of the biosurfactant was 0.1%. The addition of the biosurfactant didn't have any influence on the 5# cells. However,it could advance the 8# ones'work.5. The peak degradation of petroleum was in the first stage, and it was reduced gradually as the time run.