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Biochemical Characterization of DszD, the Flavin Reductase Involved in Bacterial Biodesulfurization

Dibenzothiophene (DBT) is a compound found in crude oil that upon combustion releases sulfur dioxide. The current chemical process used to remove sulfur from crude oil, hydrodesulfurization (HDS), is inefficient because it fails to work effectively on heterocyclic organosulfur compounds, such as DBT. Biodesulfurization (BDS) is a promising alternative to HDS for industrial sulfur removal. Microorganisms, like the bacterium Rhodococcus erythropolis, utilize BDS enzymes to remove sulfur from these organosulfur compounds while retaining the hydrocarbon structure of the fossil fuel components. In our work, we focus on the flavin reductase from the 4S BDS pathway, dibenzothiophene flavin reductase (DszD) from R. erythropolis, which catalyzes the reduction of flavin for subsequent use of dibenzothiophene monooxygenases DszC and DszA. This project entails the use of biochemical and structural experimentation to fully comprehend catalysis of DszD. DszD has been successfully overexpressed and purified to homogeneity from E. coli. Kinetic parameters have been determined using steady‐state and transient‐state kinetics. Weare currently looking at binding interactions between DszD and its substrate, DBT. Our preliminary experiments suggest that DBT may be acting as an effector; which means that DBT is selectively binding to DszD and regulating its biological activity. We plan to follow similar experiments with other sulfur‐containing compounds found in crude oil to see there is a direct interaction between substrate and DszD. Our current work will ultimately propel our research towards the long‐term goal of improving the BDS pathway for widespread industrial use.