Application of SPME/GC-MS to characterize metabolites in the biodesulfurization of organosulfur model compounds in bitumen

A combined solid-phase microextraction/GC-MS analytical technique was used to monitor the formation of metabolites in the biodesulfurization of the bitumen model organosulfur compounds, dibenzothiophene (DBT) and the dialkylated derivative 4,6-diethyldibenzothiophene (DEDBT), by Rhodococcus sp. strain ECRD-1. In the case of DBT, the following metabolites were detected: DBT 5-oxide (sulfoxide), DBT 5,5-dioxide (sulfone), dibenz[c,e][1,2]oxathiin 6-oxide (sultine), dibenz[c,e][1,2]oxathiin 6,6-dioxide (sultone), and the end product, 2-hydroxybiphenyl (2-HBP), whereas, with DEDBT, 4,6-DEDBT 5-oxide, 4,6-diethyldibenz[c,el[1,2]oxathiin 6-oxide (sultine), and 2-hydroxy-3,3'-diethylbiphenyl (HDEBP) as the final product, were identified. A time course study for the formation and disappearance of DBT and DEDBT metabolites was used to construct desulfurization pathways, which in both cases, involved the formation of the corresponding sulfoxides.