Microbial Desulfurization of Diesel Oils by Selected Bacterial Strains
Résumé
Because of increasingly stringent regulations concerning the sulfur content of motor fuels, sulfur removal by
biocatalytic means is often considered as a potential alternative to conventional deep hydrodesulfurization
processes used in the refinery industry. The first microbial strain able to selectively
oxidize sulfur of molecules such as dibenzothiophene (DBT) without altering its carbon content,
Rhodococcus erythropolis IGTS8, was isolated more than ten years ago. The metabolic pathway (4S
pathway) was elucidated and the genes involved characterized and sequenced. The present study aimed
at exploiting microbial diversity to select new strains potentially interesting for ultradeep desulfurization
of diesel oils, taking into account industrially important criteria. In a first step, 15 pure strains able to
use DBT as a sole sulfur source and to convert it to 2-hydroxybiphenyl (HBP) were obtained from
different soils. In a second step, 5 isolates belonging to the Rhodococcus/Gordonia cluster and exhibiting
good growth characteristics and high biodesulfurization activities in both aqueous and organic media
were selected. The action of resting cells from these strains towards different types of diesel oils was also
determined in order to better assess the potentiality of biodesulfurization, especially as a finishing step
complementary to deep hydrodesulfurization (HDS). Actually, in spite of their taxonomic similarity, the 5
strains displayed different activities towards the diesels oil tested. Biodesulfurization yield was also
dependent upon the diesel oil used, especially its sulfur content. Some HDS-recalcitrant compounds such
as 4,6-dimethyl dibenzothiophene, could be completely removed, but highly-alkylated dibenzothiophenes
were resistant to the action of the biocatalysts.
Domaines
Physique [physics]
Origine : Publication financée par une institution
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