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Substrate interactions in BTEX and MTBE mixtures by an MTBE-degrading isolate
1Department of Civil and Environmental Engineering, University of California, Berkeley 94720-1710, USA.
Environmental Science & Technology
|May 12, 2001
Summary
Methyl tert-butyl ether (MTBE) biodegradation is inhibited by benzene, toluene, ethylbenzene, and xylenes (BTEX). These compounds utilize independent, inducible pathways, delaying MTBE breakdown in groundwater plumes.
Area of Science:
- Environmental microbiology
- Bioremediation of fuel contaminants
Background:
- Groundwater plumes from gasoline releases often contain methyl tert-butyl ether (MTBE) and benzene, toluene, ethylbenzene, and xylenes (BTEX).
- Understanding substrate interactions is crucial for predicting contaminant fate and transport.
Purpose of the Study:
- To evaluate substrate interactions during aerobic biotransformation of MTBE and BTEX mixtures by a pure culture (PM1).
- To determine the impact of BTEX compounds on MTBE degradation by PM1.
Main Methods:
- Aerobic biotransformation experiments using a pure bacterial culture (PM1) capable of MTBE utilization.
- Exposure of MTBE-grown cells to mixtures of MTBE with individual BTEX components (benzene, toluene, ethylbenzene, xylenes) at controlled concentrations.
Main Results:
- PM1 could not degrade ethylbenzene or xylene isomers at 20 mg/L after growth on MTBE.
- Ethylbenzene and xylenes completely inhibited MTBE degradation.
- Benzene and toluene caused a lag in MTBE degradation, which resumed after BTEX compounds were nearly depleted.
- MTBE degradation slowed significantly during BTEX degradation, suggesting independent, inducible metabolic pathways.
Conclusions:
- MTBE and BTEX degradation by PM1 occur via distinct, inducible pathways.
- Subsurface microbial communities may exhibit similar inhibition patterns, delaying MTBE biodegradation until it migrates beyond BTEX plumes.