TABLE OF CONTENTS Significant research has been done since the early 1990s in the development of biodesulfurization. The majority of this work has been done in biocatalyst development, although advances in the area of process development have also been made. The major thrust for these activities was from the identification of a sulfur-specific desulfurization pathway in Rhodococcus erythropolis, sp. IGTS8 in the early 1990s. This significantly raised the potential of developing an efficient biodesulfurization process due to the selective nature of the reaction and thus, retention of the fuel value of the oil. The metabolic pathway for biodesulfurization in the organism was characterized and the enzymes necessary for the biochemical reactions were identified. Following this, the genes expressing these enzymes were also characterized and cloned into E. coli and other organisms. The rate of each step in the reaction pathway was determined, both in vivo and in vitro and the rate-limiting step was identified as the last step in the pathway involving enzyme DszB, which releases the sulfur as sulfite. All the enzymes in the pathway were overexpressed and the rate of DBT conversion was increased by over an order of magnitude. Overexpression of the enzyme DszD, which regenerates the co-factor required for the first two steps, was also achieved, further enhancing the rate of conversion (for the first two steps). The dynamics of the two enzymes, DszB and DszD, and the impact of their expression level on rate have not been studied in...
