Sulfolane degradation by mixed cultures and a bacterial isolate identified as a Variovorax sp.

Abstract.

Sulfolane (tetrahydrothiophene-1,1-dioxide) is used in the Sulfinol process for natural gas sweetening. At many sour-gas processing plants spills, landfills and leakage from unlined surface storage ponds have contaminated groundwaters with sulfolane. Due to its high water solubility and mobility in aquifers, sulfolane poses a risk for off-site contamination. This study investigated the aerobic biodegradation of sulfolane by two mixed microbial enrichment cultures and by three bacterial isolates. Sulfolane served as the sole C, S and energy source for these cultures. In the two mixed cultures, 60% and 80% of the sulfolane C was recovered as CO₂, whereas in cultures of the three isolates only 40–42% of the substrate C was recovered as CO₂. In the mixed cultures, 81% and 97% of the sulfolane S was converted to sulfate, and in the pure isolates, 55–90% of the substrate S was converted to sulfate. Thus, the mixed cultures were capable of greater mineralization than the pure isolates. One isolate, strain WP1, was identified using a combination of 16S rRNA gene sequencing, physiological traits and cell morphology. WP1 was determined to be most similar to Variovorax paradoxus.