Additionally, the effect of the coating layer on mass transfer is negligible because Idasanutlin in vivo the structure of the coating layer is looser than that of the cell wall [11]. Thus, the microbial cell/Fe3O4 biocomposite could produce a system not limited by diffusional limitations [19]. Figure 4 The carbazole biodegradation by free cells and microbial cell/Fe 3 O 4 biocomposites. A is for carbazole biodegradation. B is for the reuse of microbial cell/Fe3O4 biocomposites.

In an industrial bioremediation process, the recycle of the biocatalysts could be an important factor that determines the effectiveness of degradation for a long time. The carbazole biodegradation activities of microbial cell/Fe3O4 biocomposite were tested repeatedly.

Each test was performed until the carbazole was consumed completely. At the end of each test, the microbial cell/Fe3O4 biocomposites were collected by application of a magnetic field and then reused in another test. As shown in Figure 4B, from the first to the sixth cycle, 3,500 μg carbazole was completely consumed by microbial cell/Fe3O4 biocomposite in 9 h; from the seventh to the tenth cycle, the same amount of carbazole was completely consumed in only 2 h. It was clear that the biodegradation activity of microbial cell/Fe3O4 biocomposites increased GSK2118436 mouse gradually during the recycling processes, which may be due to that more microbial cells was immobilized by Fe3O4 nanoparticles with the microbial cell growth and reproduction. Additionally,

carbazole can be quickly transferred to the biocatalyst surface where nanosorbents were located and resulted in the increase of biodegradation rate [10, 14]. These results are different from other researchers’ report which stated that the desulfurization activity of microbial cells coated by magnetite nanoparticles decreased gradually after a few test cycles [11]. Conclusions In conclusion, the microbial cell/Fe3O4 biocomposite was evaluated as a novel aspect of the industrialization of microbial cell immobilization. Moreover, magnetic (Fe3O4) nanoparticles have a large specific surface and super-paramagnetic properties, which not only reduced the mass transfer resistance of traditional immobilization RVX-208 method, but also facilitated the recovery of immobilized cells in the reuse process. Additionally, the recycle experiments demonstrated that the biodegradation activity of microbial cell/Fe3O4 biocomposites increased gradually during the recycling processes. These results indicated that magnetically modified microbial cells provide a JAK inhibitor promising technique for improving biocatalysts used in the biodegradation of hazardous organic compounds. Acknowledgements This work was supported by grants from the National Natural Science Foundation of China (21177074), Excellent Middle-Aged and Youth Scientist Award Foundation of Shandong Province (BS2010SW016), and New Teacher Foundation of Ministry of Education of China (20090131120005).