Sulfolobus acidocaldarius Sulfur

In the context of the desirability of removing sulfur compounds from fuels, a bacterial strain has been identified that will metabolize thianthrene to water-soluble products under aerobic conditions (83MI5). A thermophilic organism, Sulfolobus acidocaldarius, removed 38% of the sulfur, as measured by sulfate release, in 4 weeks at 70°C (87MI2). 

Working with a mutated bacterial strain, Isbister et al. (62) demonstrated a novel mechanism of aerobic oxidation of dibenzothiophene which involved the specific excision of the sulfur atom from the molecule (Figure 11). Studies with -labeled dibenzothiophene showed the release of the radioactivity into the aqueous phase and ion chromatography showed the appearence of sulfate. There was no radioactive carbon dioxide released when this microorganism was incubated with 14C-labeled dibenzothiophene. GC-MS analysis showed that the oxidation product was 2,2 -dihydroxybiphenyl. Kargi and Robinson (52) also report the release of sulfate from dibenzothiophene. This OSC served as the sole carbon and sulfur source in their cultures of the aerobic thermophile Sulfolobus acidocaldarius. 

Other work that has been carried out with microbial devulcanisation includes use of the microorganism Pyrococcus furiosus to carry out devulcanisation under anaerobic conditions. This type of bacteria reduces the sulfur in the crosslinks to hydrogen sulfide [108]. Another type of bacteria, Sulfolobus acidocaldarius, can be used to selectively cleave carbon-sulfur bonds to generate sulfate compounds that stay in the rubber and so the sulfur remains available for any revulcanisation treatments [109]. 

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