Chapter 1: EMERGING MICROBIAL DIBENZOTHIOPHENE DESULFURIZATION FOR FUEL

Our research focus is to isolate microbial biocatalyst using dibenzothiophene as model compound with practical
approach to biodesulfurization of petroleum. Isolates were obtained from soil
microcosm, culture enrichment with dibenzothiophene (DBT), selection for fluorescence
under UV light for the presence of phenol, 2-hydroxybiphenyl (2-HBP), staining using 4-
aminoantipyrene and purification using thermal induction. Culture isolates were preadapted
in diesel by surface growth exposure. UV absorbance scanning was with a
recording spectrophotometer to identify 2-HBP spectra of the isolates.
Biodesulphurization of commercial feedstock using strain biomass were done in
agitated flasks with buffer at 45 oC. Samples were processed for GC-MS/ or FTIR. One
primary isolate, 3Jn screened positive for phenol, showed similar UV spectra of 2-HBP,
the main product of 4S multienzyme pathway for aerobic desulfurization.
Biodesulphurization activity depressed by yeast extract appeared to be temperature
dependent. The 18 purified, facultative thermo strains were active to both two-ring,
benozothiophene (BT) and three-ring, DBT organic sulfur compounds and thus could be
widely used as “cleaning” desulfurizing agents. Strains showed differences in
“expression” of DBT or BT with opposing orientation, which suggested that activity with
organic sulphur compounds was "competitive". However, isolates without significant
difference in activity were also detected to as much as 67% or greater than 39% among
the strains selected. FTIR analyses showed reduction in spectral signals with microbial
treatment. Biodesulphurization based on the optical density of spent media from treated
feedstock showed more than 2x activity compared to controls.