Response Surface Methodology Optimization of Dibenzothiophene Biodesulfurization in Model Oil by Nanomagnet Immobilized Rhodococcus Erythropolis R1

Rhodococcus erythropolis R1 is a capable strain in bioconversion of dibenzothiophene (DBT) to 2-hydroxybiphenyl (2-HBP) in oil model. In order to prevent the contamination of biodesulfurization (BDS) products by free cells, microbial cells were immobilized using different materials such as magnetic Fe3O4 nanoparticles (NPs). In this study, magnetic NPs were produced by two different procedures and their characteristics were determined via transmission electron microscopy (TEM) and X-ray diffraction (XRD). Also, binding of NPs on the cell surface was studied and better NPs were used for cells immobilization. Both NPs were crystallized and less than 10nm. The BDS by immobilized cells was carried out in biphasic system, and media conditions were optimized statistically by response surface methodology (RSM). The DBT concentration, temperature and interaction between them had statistically significant effects on 2-HBP production by nanomagnet immobilized cells. The optimum DBT concentration, temperature and pH for 2-HBP production by immobilized R. erythropolis R1 were obtained at 6.76mM, 29.63 °C and 6.84 respectively by HPLC analysis.