Study On Laser Irradiation Breeding And Kinetics Of Dibenthiophene Biodesulfurization By Rhodococcus Sp

Combustion of petroleum-derived fuels leads to the atmospheric emission of sulfur oxides, which are the major cause of acid rain. The traditional hydrodesulfurization (HDS) is performed at high pressures and temperature, leading to increased operation and capital costs. Also, HDS cannot remove the sulfur from the most recalcitrant molecules effectively and economically. Biodesulfurization (BDS) can selectively desulfurize the sulfur from the most recalcitrant under the mild conditions, remaining the combustion value of the fuels. Thus BDS can offer an attractive alternative to HDS process. A strain, namely EBT-2, was isolated from the wastewater of Dagang oil field with the ability to desulfurize dibenthiophene (DBT) through the 4S pathway. The strain showed high abilities both to DBT-desulfurization in aqueous system and to desufurization in fuel oil. The morphologic and taxonomic properties of the strain were investigated, and the strain belonged to Rhodococcus sp. according to Bergey's Manual of Determinative Bacteriology. Laser was employed to irradiate the cells of the strain EBT-2 to obtain the mutant with the higher ability to desulfurize DBT. When energy dose and output power were 22.9 J/cm2 and 20mW, respectively, a positive mutant strain, Rhodococcus sp. EBT-2A, was acquired. In comparison with the initial strain EBT-2, the biodesulfrization capacity of the mutant strain EBT-2A was enhanced by 20%. Furthermore, the kinetics of DBT-desulfurization by both the mutant strain EBT-2A and the initial strain EBT-2A was studied with resting cells in aqueous phase. Michaekis-Menten equation was adopted and the kinetic parameters were derived based on the experimented data, μmax=173.0 nmol DBT/(g DCW·min), KS=447.8nmol/L for the initial strain EBT-2, and μmax=225.0 nmol DBT/(g DCW·min), KS= 226.2 nmol/L for the mutant strain EBT-2A. The regressed equation fitted the experimental data well.