Edinburgh Napier University

  Petro-chemically derived fuels may contain a range of organosulfur compounds that produce sulfur dioxide when combusted, culminating in atmospheric and soil pollution. Sulfur constituents include thiophenes, such as Benzothiophene and Dibenzothiaphene(DPT), with the latter often used as a model for the isolation of bacteria capable of selective removal of sulfur for potential use in the desulfurization of fuel oils. A bacterium capable of desulfuring DBT was isolated from a gasoline-contaminated soil in Isfahan,Iran. Desulfurization employs the 4S metabolic pathway that leads to the production of 2-hydroxybiphenyl (HBP) as an end product. Biochemical analyses and 16S rRNA gene sequencing identified the organism as Rhodococcus erythropolis(strain R1) with a rapid capability to desulfurize DBT when using it as its sole sulfur source. Plasmids from R.erythropolis strain R1 (HBP-positive) were used to produce a stable desulfurizing mutant (mut23) of a HBP-negative strain by polyethylene glycol (PEG)-mediated protoplast transformation. R.erythropolis strain R1 and transformed Rhodococcus strain (mut23) were able to degrade 100% of the original DBT after 72h. However, mut23 desulfurized DBT and produced HBP more efficiently than wild type R1 strain.