Biodesulfurization has been an area of active research for the past few decades, in an effort to curb the amount of sulfur byproducts released... Show moreBiodesulfurization has been an area of active research for the past few decades, in an effort to curb the amount of sulfur byproducts released into the environment. One key aspect of sulfur removal using biological techniques is the microbial conversion/utilization of dibenzothiopene (DBT), an ubiquitous component of organic sulfur compounds of crude oil. Three main enzymes are involved in 4S pathway of biodesulfurization; they are DszA, DszB, and DszC. DszD is a fourth enzyme that provides the necessary cofactors to Dsz A and DszC to complete their monooxygenase reactions in a number of bacteria with desulfurization capability, such as Rhodococcus erythropolis IGTS8. In this study, two ways to engineer bacteria, especially E. coli, for improved biodesulfurization of crude oil were investigated. The first was to express the dszD gene in E. coli in conjunction with the dszABC operon and study its effect on the growth pattern of the cells in minimal medium with DBT as the sole source of sulfur. The second approach was to clone the gene encoding sulpeptide S2, which is a sulfur-rich polypeptide, along with the desulfurization operon so that expression of sulpeptide would increase the demand for sulfur by the host cells. dszD and S2 were successfully cloned downstream of existing constructs of pGEM T-easy dszABC and pNW33N dszABCD and were expressed in E. coli strains BL21 and DH5α respectively. Growth experiments indicated marginal increase in the presence of dszABC compared to the unengineered strain and in the presence of dszD and S2; however, improved desulfurization activity was observed in the case of cells harboring dszD in addition to the dszABC operon. M.S. in Biology, May 2011 Show less
