Multi-criteria comparison of resting cell activities of bacterial strains selected for biodesulfurization of petroleum compounds

Five isolates able to utilize dibenzothiophene (DBT) as a sole sulfur source and to convert it to 2-hydroxybiphenyl (HBP) with high rates were selected to investigate their potentialities as biocatalysts of a diesel oil biodesulfurization process. Conventional and chemotaxonomic analyses and 16S ribosomal DNA (rDNA) sequencing showed that these strains belonged to the Rhodococcus/Gordonia cluster. The desulfurizing activities of resting cells were compared under various conditions to evaluate their stability in both aqueous and organic media, their sensitivity to the presence of hexadecane and their sulfur substrate selectivity. In spite of their taxonomic similarity, the five strains exhibited different properties. This diversity was not confirmed by the analysis of the desulfurizing genes by amplification and sequencing of large fragments of dszA, dszB, dszC, and dszD genes which revealed that four of the five selected strains had a dsz genotype identical to those of the reference strain, Rhodococcus erythropolis IGTS8.