Biodesulfurization of dibenzothiophene in Escherichia coli is enhanced by expression of a Vibrio harveyi oxidoreductase gene

One possible alternative to current fuel hydrodesulfurization methods is th e use of microorganisms to remove sulfur compounds. Biodesulfurization requ ires much milder processing conditions, gives higher specificity, and does not require molecular hydrogen. In the present work we have produced two co mpatible plasmids: pDSR3, which allows Escherichia coil to convert dibenzot hiophene. (DBT) to hydroxybiphenyl (HBP), and pDSR2, which produces a Vibri o harveyi flavin oxidoreductase. We show that the flavin oxidoreductase enh ances the rate of DBT removal when co-expressed in vivo with the desulfuriz ation enzymes. The plasmids pDSR2 and pDSR3 were co-expressed in growing cu ltures. The expression of oxidoreductase caused an Increase in the rate of DBT removal but a decrease in the. rate of HBP production. The maximum rate of DBT removal was 8 mg/h . g dry cell weight. Experiments were also condu cted using resting cells with the addition of various carbon sources. It wa s found that the addition of glucose or glycerol to cultures with oxidoredu ctase expression produced the highest DBT removal rate (51 mg/h g dry cell weight). The culture with acetate and no oxidoreductase expression had the highest level of HBP production. For all carbon sources, the DBT removal ra te was faster and the HBP generation rate slower with the expression of the oxidoreductase. Analysis of desulfurization intermediates indicates that t he last enzyme in the pathway may be limiting. (C) 2000 John Wiley & Sons, Inc.