Application of solid-phase extraction to the analysis of the isomers generated in biodesulfurization against methylated dibenzothiophenes

A solid-phase extraction (SPE) technique was applied to analyze and characterize the biodesulfurization reactions against asymmetrically methylated dibenzothiophenes (mDBTs) such as 1-, 2-, 3- and 4-methyldibenzothiophenes present in fossil fuels. Recently, we found that these mDBTs are efficiently degraded by the bacterial strain, Rhodococcus erythropolis KA2-5-1. Separation and concentration of the microbial desulfurization products from each of the mDBTs could be carried out with high efficiency and reproducibility by the SPE procedure. These desulfurization products were identified using the SPE technique combined with GC, GC–atomic emission detection, GC–MS and 1H nuclear magnetic resonance spectroscopy. The analytical data obtained suggested that the desulfurization reactions against mDBTs by this bacterial strain may occur through specific carbon–sulfur bond-targeted cleavages that can be affected by the positions of methyl groups.