Transformation of non-oxygenated, homocyclic aromatic compounds by aquifer microorganisms under methanogenic and sulfate-reducing conditions

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:5295568

Edwards, E A

A mixed methanogenic culture was enriched from creosote-contaminated sediment that used toluene or o-xylene as sole source of carbon and energy. The adaptation periods before the onset of measurable degradation were long (120-255 days). Both toluene and o-xylene were completely degraded to stoichiometric amounts of methane, carbon dioxide and biomass. The enriched methanogenic cultures could not degrade benzene, m-xylene, p-xylene or ethylbenzene. The doubling times were 6 days and 10 days for the cultures growing on toluene or o-xylene, respectively. Toluene and o-xylene were toxic and inhibited degradation as initial concentrations increased. The presence of preferred substrates including glucose, methanol, and acetate inhibited toluene degradation. Isotope trapping and simultaneous adaptation experiments provided evidence that toluene was degraded via both methyl and ring hydroxylation. A mixed sulfate-reducing culture was enriched from gasoline-contaminated sediment that used toluene and all three isomers of xylene as sole sources of carbon and energy. The adaptation period before the onset of measurable degradation by the sulfate-reducing cultures was followed sequentially by m-, p-, and o-xylene. The doubling time for the sulfate-reducing cultures growing on toluene or xylenes was about 20 days. The build up of sulfide as a result of sulfate-reduction appeared to inhibit degradation. Benzoate was detected as a transient intermediate and benzylsuccinate accumulated in sulfate-reducing cultures fed toluene. Benzene degradation was not initially observed. However, after all other carbon sources were exhausted benzene was eventually completely mineralized to carbon dioxide under strictly anaerobic conditions. The rates of degradation were very slow, and were influenced by the initial benzene concentration and by the presence of other carbon sources that could be degraded preferentially over benzene.

• Research Organization: Stanford Univ., CA (United States)
• OSTI ID: 5295568
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540220 -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
550500* -- Metabolism
59 BASIC BIOLOGICAL SCIENCES
ALKYLATED AROMATICS
ANAEROBIC CONDITIONS
AROMATICS
BACTERIA
BENZENE
BIODEGRADATION
CHEMICAL REACTIONS
CREOSOTE
DECOMPOSITION
HYDROCARBONS
HYDROXYLATION
MICROORGANISMS
MINERALIZATION
ORGANIC COMPOUNDS
RESPONSE MODIFYING FACTORS
SULFATE-REDUCING BACTERIA
TIME DEPENDENCE
TOLUENE
XYLENES