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Appl. Environ. Microbiol., Aug 1997, 3032-3042, Vol 63, No. 8
KG Kropp, JT Andersson and PM Fedorak
The transformations of 1,2,3,4-tetrahydrodibenzothiophene (THDBT) were
investigated with pure cultures of hydrocarbon-degrading bacteria.
Metabolites were extracted from cultures with dichloromethane (DCM) and
analyzed by gas chromatography (GC) with flame photometric, mass, and
Fourier transform infrared detectors. Three 1-methylnaphthalene
(1-MN)-utilizing Pseudomonas strains oxidized the sulfur atom of THDBT to
give the sulfoxide and sulfone. They also degraded the benzene ring to
yield 3-hydroxy-2-formyl-4,5,6,7-tetrahydrobenzothiophene. A cell
suspension of a cyclohexane-degrading bacterium oxidized the alicyclic ring
to give a hydroxy-substituted THDBT and a ketone, and it oxidized the
aromatic ring to give a phenol, but no ring cleavage products were
detected. GC analyses with an atomic emission detector, using the
sulfur-selective mode, were used to quantify the transformation products
from THDBT and dibenzothiophene (DBT). The cyclohexane degrader oxidized
19% of the THDBT to three metabolites. The cometabolism of THDBT and DBT by
the three 1-MN-grown Pseudomonas strains resulted in a much greater
depletion of the condensed thiophenes than could be accounted for in the
metabolites detected by GC analysis, but there was no evidence of sulfate
release from DBT. These 1-MN-grown strains transiently accumulated
3-hydroxy-2-formylbenzothiophene (HFBT) from DBT, but it was subsequently
degraded. On the other hand, Pseudomonas strain BT1d, which was maintained
on DBT as a sole carbon source, accumulated 52% of the sulfur from DBT as
HFBT over 7 days, and, in total, 82% of the sulfur from DBT was accounted
for by the GC method used. Lyophilization of cultures grown on 1-MN with
DBT and methyl esterification of the residues gave improved recoveries of
total sulfur over that obtained by DCM extraction and GC analysis. This
suggested that the further degradation of HFBT by these cultures leads to
the formation of organosulfur compounds that are too polar to be extracted
with DCM. We believe that this is the first attempt to quantify the
products of DBT degradation by the so-called Kodama pathway.
Copyright © 1997, American Society for Microbiology
Bacterial Transformations of 1,2,3,4-Tetrahydrodibenzothiophene and Dibenzothiophene
Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada, and Department of Analytical Chemistry, University of Munster, D-48149 Munster, Germany
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