Sequencing, cloning and expression of the dsz genes required for dibenzothiophene sulfone desulfurization from Gordonia alkanivorans strain 1B

Biological desulfurization of fossil fuels may offer an alternative process to reduce sulfur dioxide emissions that cause environmental pollution. Gordonia alkanivorans strain 1B is able to convert dibenzothiophene sulfone (DBTS) to 2-hydroxybiphenyl (2-HBP), the final product of 4S pathway. G. alkanivorans genes that code for the enzymes involved in this degrading pathway were PCR amplified using homologous primers based on known sequences from Rhodococcus erythropolis IGTS8. Amplified fragments were further cloned and sequenced. Strain 1B desulfurization genes (dsz) were identified and compared with previously described bacterial genes from other strains. Three open reading frames were identified (dszA, dszB and dszC) and have shown high similarity when compared to those from R. erythropolis IGTS8 (88% for dszA, 88% for dszB and 90% for dszC). G. alkanivorans dszAB genes were further expressed in Escherichia coli. This recombinant strain was able to grow in a culture medium containing dibenzothiophene sulfone (DBTS) as the only sulfur source desulfurizing the same amount of DBTS (0.2 mM) to 2-HBP but 4.5-fold faster than strain 1B. In addition, the recombinant strain could also desulfurize DBTS in LB medium containing other sulfur compounds such as sulfates, showing no sulfate repression of the dszAB genes expression.