There exists three-phase (diesel oil/bacteria cell/aqueous phase)O/W emulsion after diesel oil biodesulfurization(BDS).For commercial application

the emulsion must be de-emulsified to yield diesel oil after BDS.In fact

this is the last process of BDS.Several de-emulsifiers applicable to this three-phase O/W emulsion

such as several typical water-soluble de-emulsifiers

methanol

ethanol

and the Rhodococcus sp. pellets which can desulfurize diesel oil were tested.Ethanol was the best

and the de-emulsification mechanism with different de-emulsifiers was discussed. 4% ethanol

as a de-emulsifier could separate oil by centrifuge because of its strong surfactivity

high hydrophilic property and appropriate density.The diesel oil recovery could be increased by centrifugal separation from 60% to almost 100%.GC-MS analysis showed ethanol addition for de-emulsification did not affect the composition of alkenes.It was also noted that the pellets of DS-3 centrifuged showed the same growth rate and dibenthiophene desulfurization activity as the original bacteria

so they could be re-used as desulfurization biocatalyst.