Biodegradation of MTBE: the effect of environmental factors (original) (raw)
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Biodegradation, 2000
With the current practice of amending gasoline with up to 15% by volume MTBE, the contamination of groundwater by MTBE has become widespread. As a result, the bioremediation of MTBE-impacted aquifers has become an active area of research. A review of the current literature on the aerobic biodegradation of MTBE reveals that a number of cultures from diverse environments can either partially degrade or completely mineralize MTBE. MTBE is either utilized as a sole carbon and energy source or is degraded cometabolically by cultures grown on alkanes. Reported degradation rates range from 0.3 to 50 mg MTBE/g cells/h while growth rates (0.01-0.05 g MTBE/g cells/d) and cellular yields (0.1-0.2 g cells/g MTBE) are generally low. Studies on the mechanisms of MTBE degradation indicate that a monooxygenase enzyme cleaves the ether bond yielding tert-butyl alcohol (TBA) and formaldehyde as the dominant detectable intermediates. TBA is further degraded to 2-methyl-2-hydroxy-1propanol, 2-hydroxyisobutyric acid, 2-propanol, acetone, hydroxyacteone and eventually, carbon dioxide. The majority of these intermediates are also common to mammalian MTBE metabolism. Laboratory studies on the degradation of MTBE in the presence of gasoline aromatics reveal that while degradation rates of other gasoline components are generally not inhibited by MTBE, MTBE degradation could be inhibited in the presence of more easily biodegradable compounds. Controlled field studies are clearly needed to elucidate MTBE degradation potential in co-contaminant plumes. Based on the reviewed studies, it is likely that a bioremediation strategy involving direct metabolism, cometabolism, bioaugmentation, or some combination thereof, could be applied as a feasible and cost-effective treatment method for MTBE contamination.
World Journal of Microbiology and Biotechnology, 2006
Methyl tert-Butyl Ether (MTBE) has been used in gasoline as a substitute for lead-based additives, which have been demonstrated to be toxic. MTBE however, is persistent in soil and water, showing high affinity for water and low affinity for soil, and has become an important contaminant. Therefore, the aim of this work was to isolate and identify soil microorganisms capable of degrading MTBE. Two samples were taken from a gasoline-contaminated soil at a service station and 59 different bacterial strains were isolated by enrichment culture with three consecutive selective transfers. Biochemical and morphological characterization of the bacterial isolates classified them into the following groups: Bacillus, Rhodococcus, Micrococcus, Aureobacterium and Proteus. Twelve strains were selected for evaluation of MTBE biodegradation depending on visual growth and biomass production of the isolates in minimal salt broth. Six strains significantly reduced MTBE concentration (22-37%) compared to an abiotic control after 5 days of incubation. Although it has been considered that MTBE is degraded mainly by cometabolism, our results demonstrate that these microorganisms are able to reduce MTBE concentration when MTBE is the sole source of carbon.
Bioremediation of MTBE: a review from a practical perspective
Biodegradation, 2000
The addition of methyl tert-butyl ether (MTBE) to gasoline has resulted in public uncertainty regarding the continued reliance on biological processes for gasoline remediation. Despite this concern, researchers have shown that MTBE can be effectively degraded in the laboratory under aerobic conditions using pure and mixed cultures with half-lives ranging from 0.04 to 29 days. Ex-situ aerobic fixed-film and aerobic
In situ MTBE biodegradation supported by diffusive oxygen release
Environmental science & …, 2002
Microcosm studies with sediments from Vandenberg Air Force Base, CA, suggest that native aerobic methyl tertbutyl ether (MTBE)-degrading microorganisms can be stimulated to degrade MTBE. In a series of field experiments, dissolved oxygen has been released into the anaerobic MTBE plume by diffusion through the walls of oxygenpressurized polymeric tubing placed in contact with the flowing groundwater. MTBE concentrations were decreased from several hundred to less than 10 µg/L during passage through the induced aerobic zone, due apparently to in situ biodegradation: abiotic MTBE loss mechanisms were insignificant. Lag time for initiation of degradation was less than 2 months, and the apparent pseudo-first-order degradation rate was 5.3 day -1 . Additional MTBE was added in steps to raise the influent concentration to a maximum of 2.1 mg/L. With each step, MTBE was degraded within the preestablished aerobic treatment zone at rates ranging from 4.4 to 8.6 day -1 . Excess dissolved oxygen suggested that even higher MTBE concentrations could have been treated. Continued flow through the treatment zone was repeatedly confirmed through tracer and other tests. These and others' results suggest that it is possible to create permeable in situ treatment zones solely by releasing oxygen to support native microbial degradation of MTBE.
Biodegradation of MTBE by bacteria isolated from gasoline-contaminated sites
2004
Methyl tertiary butyl ether (MTBE) belongs to the group of gasoline oxygenates and persistent environment contaminants, and shows potential for biodegradation in aerobic and anaerobic conditions, through application of pure microbial cultures. Presented research shows that indigenous bacterial isolates 6sy and 24p, selected from oil hydrocarbons-contaminated environments, were capable of utilizing MTBE as sole carbon and energy source. Based on 16S rDNA sequence analysis, bacterial isolates 6sy and 24p were identified as Staphylococcus saprophyticus subsp. saprophyticus and Pseudomonas sp., respectively. The MTBE biodegradation rate was affected by longevity of incubation period and initial MTBE concentration. After 3 weeks of incubation at 25°C in a dark, the removal rates of initial 25 and 125 ppm MTBE concentrations by Staphylococcus saprophyticus 6sy were found to be 97, and 63%, respectively, while efficiency of Pseudomonas sp. in degradation of indicated concentrations was 96, and 40%, respectively. Both bacterial isolates were able to grow in MTBE-containing growth medium. Highest growth rate of bacterial isolates was observed at the end of incubation period. The presented results indicated the potential of these bacterial isolates in bioremediation of MTBE-contaminated environments.
Methyl tert-butyl ether (MTBE) bioremediation studies
2000
The massive production of methyl tert-butyl ether (MTBE), a primary con- stituent of reformulated gasoline, combined with its mobility, persistence and toxicity, makes it an important pollutant. It was considered recalcitrant until a few years ago, but recently MTBE biodegradation in aerobic conditions has been demonstrated with both mixed and pure cultures. Mixed cultures are generally the more effective for
FEMS Microbiology Ecology, 2000
Eleven soil samples (contaminated and non-contaminated top soils and aquifers) from seven different locations in Belgium were examined in lab-scale batch microcosms simulating in situ conditions for their indigenous capacity to biodegrade methyl tert-butyl ether (MTBE). The effect of implementing nutrients or additional oxygen and of the presence of co-contaminants on MTBE degradation was investigated. All soils showed rapid degradation of benzene. On the other hand, only one site, historically contaminated with oxygenated fuel, provided soil samples showing relatively fast MTBE biodegradation. These soil samples originated from four different depths from the vadose and saturated zone. MTBE degradation kinetics differed between the samples of the saturated and non-saturated zone and depended on the implemented conditions. MTBE-biodegradation in the samples from the non-saturated zone started after a very short lag-phase (<7 days), while long lag-phases (up to 270 days) were obtained with the other samples. Addition of extra nutrients stimulated MTBE degradation kinetics in microcosms containing the saturated soil samples while inhibiting effects were seen in the case of non-saturated soil samples. In contrast, implementing dissolved oxygen concentrations of 9.5 and 11.5 mg l À1 led to lower degradation kinetics compared to 8 mg l À1 in microcosms containing saturated soil samples, while stimulating effects were seen with the non-saturated soil samples. Addition of an extra carbon source like benzene or propane did increase in general the MTBE first order degradation rate constant. Differences in the eubacterial community composition between these depth samples were confirmed based on denaturing gradient gel electrophoresis (DGGE) patterns of PCR-amplified 16S rRNA gene fragments. The results of the presented study indicate that an aerobic MTBE biodegradation potential is not omnipresent in Belgian sub-soils.
Ground Water Monitoring & Remediation, 2007
Compound specific isotope analysis (CSIA) was used to investigate biodegradation of trichloroethene (TCE) and methyl tert-butyl ether (MTBE) at contaminated field sites in Alaska and New York State, respectively. At both sites, geochemical conditions and the presence of metabolic intermediates (cis-1-2-dichloroethene and tert-butyl alcohol [TBA]) suggested the potential for biodegradation of TCE and MTBE, respectively. Given that in both cases these metabolic intermediates could also have been present as cocontaminants in the source zone, CSIA was undertaken to evaluate the possibility of in situ biodegradation. At the TCE-contaminated field site in Alaska, d 13 C values of TCE in ground water determined in this study showed no evidence of biodegradation (mean d 13 C of À27.0 6 1.0& for nine wells), and quantitative-polymerase chain reaction analyses of ground water from four wells found no evidence of dechlorinator Dehalococcoides sp. at this site. At the MTBE-contaminated field site in New York, TBA was present in the ground water but was not present in gasoline sampled from underground storage tanks (UST) on-site, suggesting that at this site, TBA was potentially a metabolite of MTBE biodegradation rather than a cocontaminant. However, at all sampling times and locations, d 13 C and d 2 H values of MTBE in ground water were within range of published values for undegraded MTBE in gasoline. While the occurrence of a small extent of in situ MTBE biodegradation cannot be ruled out, the findings suggest that it is more likely that multiple gasoline spills occurred through time, and while present day USTs do not contain TBA as a cocontaminant, gasoline spilled at the site in the past may have. At both contaminated field sites, CSIA, chemical, and microbiological lines of evidence suggest that biodegradation was not a significant attenuation process. The results of these two studies underscore the need for an integrated approach to site assessment that draws on measurements of metabolic intermediates, analysis of stable isotopes, and microbial evidence to give a reliable assessment of in situ biodegradation at contaminated field sites.
Biodegradation of MTBE by Bacteria Isolated from oil Hydrocarbons- Contaminated Environments
Methyl tertiary butyl ether (MTBE) belongs to the group of gasoline oxygenates and persistent environment contaminants, and shows potential for biodegradation in aerobic and anaerobic conditions, through application of pure microbial cultures. Presented research shows that indigenous bacterial isolates 6sy and 24p, selected from oil hydrocarbons-contaminated environments, were capable of utilizing MTBE as sole carbon and energy source. Based on 16S rDNA sequence analysis, bacterial isolates 6sy and 24p were identified as Staphylococcus saprophyticussubsp. saprophyticusand Pseudomonas sp., respectively. The MTBE biodegradation rate was affected by longevity of incubation period and initial MTBE concentration. After 3 weeks of incubation at 25°C in a dark, the removal rates of initial 25 and 125 ppm MTBE concentrations by Staphylococcus saprophyticus6sy were found to be 97, and 63%, respectively, while efficiency of Pseudomonas sp. in degradation of indicated concentrations was 96, and 40%, respectively. Both bacterial isolates were able to grow in MTBE-containing growth medium. Highest growth rate of bacterial isolates was observed at the end of incubation period. The presented results indicated the potential of these bacterial isolates in bioremediation of MTBE-contaminated environments.