Kinetics of desulfurization by Rhodococcus erythropolis SHT۸۷

Background and Aim : Biodesulfurization is using living systems to reduce sulfur content in fossil fuels at moderate pressure and temperature conditions. Here, the pattern of dibenzothiophene (DBT) reduction by using Rhodococcus erythropolis SHT۸۷, was studied.Methods : Solutions, containing ۰.۱ to ۶.۵ mM DBT in n-Tetradecane, were used to study the biodesulfurization process by this bacterium. The resting cells of Rhodococcus erythropolis SHT۸۷, were added to the reaction mixture up to ۱۰ gDCW/L. Then, the specific desulfurization activities in the first two hours were determined by HPLC (with a C۱۸ column). The mobile phase was a ۴:۱ mix of acetonitrile: water at ۱.۸ ml/min). All statistical analyses were performed by using GraphPad Prism software.Results : The results show the hyperbolic relationship between the specific desulfurization activity and the initial concentrations of DBT. It shows that the biodesulfurization process by this bacterium follows the Michaelis–Menten kinetics in these conditions. Vmax and Michaelis constant (Km) were estimated ۰.۵۱ micromol/gDCW/min and ۰.۳۴ mM.Conclusion : Such a relationship between the specific desulfurization activity of the resting cells and the initial concentration of DBT has been reported many times in different desulfurizing microorganisms. In previous reports for other cells, different values from ۰.۰۴ to ۳ micromol/gDCW/min have been shown for Vm. So, it can be said that the maximum velocity of biodesulfurization by SHT۸۷ is appropriate and acceptable. Km in this research is less than the same parameter in many other experiments, which have been done by the other members of Rhodococcus and by Pseudomonas strains.

Keywords:

Biodesulfurization , Rhodococcus erythropolis SHT۸۷ , Kinetics