In situ cell separation and immobilization method for dibenzothiophene biodesulfurization was developed by using superparamagnetic Fe₃O₄ nanoparticles. Magnetic Fe₃O₄ nanoparticles were synthesized by a coprecipitation method followed by modification with ammonium oleate. The surface-modified Fe₃O₄ nanoparticles were monodispersed in an aqueous solution, and the average particle size was about 20 nm with 50.8 emu/g saturation magnetization (d_s). After adding the magnetic fluids to the culture broth, the microbial cells of Rhodococcus erythropolis LSSE8-1 was adsorptive immobilized and then separated by external application of a magnetic field. The maximum adsorption amount was about 530 g dry cell weight/g particles. Transmission electron microscopy (TEM) analysis of the cells showed that the Fe₃O₄ nanoparticies were strongly absorbed to the surfaces and coated the cells.

The coated cells had distinct superparamagnetic properties, with the d_s was 14.0 emu/g. Compared to the reusable limitation of the free cells, the coated cells not only had the same desulfurizing activity as free cells but could also be reused more than six times. The one-step magnetic immobilized LSSE8-1 cells exhibited good catalytic activity and repeated-batch desulfurization operational stability. The mechanism of cell adsorption on oleate-coated Fe₃O₄ nanoparticles was also discussed.

References

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