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Notice of Retraction
After careful and considered review of the content of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE's Publication Principles.
We hereby retract the content of this paper. Reasonable effort should be made to remove all past references to this paper.
The presenting author of this paper has the option to appeal this decision by contacting TPII@ieee.org.
Effect of biosurfactant-rhamnolipid at different concentrations on the growth, protein release, and the cell hydrophobicity of Pseudomonas sp. HC15 and Pseudomonas sp. HD17 on n-octadecane were studied. Higher concentration of rhamnolipid (30 and 50 mg·L-1) inhibited the growth of these two strains and caused higher levels of extracellular protein release, and only 10 mg·L-1 rhamnolipid increased the biomass of Pseudomonas sp. HC15, which showed that these two strains were very sensitive to biosurfactant-rhamnolipid. Furthermore, higher concentration of rhamnolipid could improve the cell hydrophobicity in the exponential phase growth of the two strains. Scanning-electron-microscopy results showed that 50 mg·L-1 biosurfactant-rhamnolipid had a strong disruptive effect on the cell membrane compared to the cells that were not treated with rhamnolipid. On the other hand, the surface tension of the culture medium supernatant did not change obviously. The experiment indicated the possibility that the mechanism of direct uptake of insoluble n-octadecane occurred in our experiment in addition to uptake the pseudosolubilization smaller oil droplets, which might be related to the bacteria that we used. The results of this work appeared, however, that low concentrations of biosurfactant-rhamnolipid must be applied carefully in the bioremediation process.