Modern geochemical and molecular tools for monitoring in-situ biodegradation of MTBE and TBA

Kuder, Tomasz; Philp, Paul

doi:10.1007/s11157-007-9123-6

Cited by 9 publications

(4 citation statements)

References 69 publications

(90 reference statements)

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“…Recently, compound-specific stable isotope analysis (CSIA) for identification and quantification of in situ biodegradation of MTBE and related compounds has been proposed (27,40,50,56). However, this method requires special analytical equipment.…”

Section: Discussionmentioning

confidence: 99%

Formation of Alkenes via Degradation of tert -Alkyl Ethers and Alcohols by Aquincola tertiaricarbonis L108 and Methylibium spp

Schäfer

Muzica

Schuster

et al. 2011

Appl Environ Microbiol

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Bacterial degradation pathways of fuel oxygenates such as methyl tert-butyl and tert-amyl methyl ether (MTBE and TAME, respectively) have already been studied in some detail. However, many of the involved enzymes are still unknown, and possible side reactions have not yet been considered. In Aquincola tertiaricarbonis L108, Methylibium petroleiphilum PM1, and Methylibium sp. strain R8, we have now detected volatile hydrocarbons as by-products of the degradation of the tert-alkyl ether metabolites tert-butyl and tert-amyl alcohol (TBA and TAA, respectively). The alkene isobutene was formed only during TBA catabolism, while the beta and gamma isomers of isoamylene were produced only during TAA conversion. Both tert-alkyl alcohol degradation and alkene production were strictly oxygen dependent. However, the relative contribution of the dehydration reaction to total alcohol conversion increased with decreasing oxygen concentrations. In restingcell experiments where the headspace oxygen content was adjusted to less than 2%, more than 50% of the TAA was converted to isoamylene. Isobutene formation from TBA was about 20-fold lower, reaching up to 4% alcohol turnover at low oxygen concentrations. It is likely that the putative tert-alkyl alcohol monooxygenase MdpJ, belonging to the Rieske nonheme mononuclear iron enzymes and found in all three strains tested, or an associated enzymatic step catalyzed the unusual elimination reaction. This was also supported by the detection of mdpJK genes in MTBE-degrading and isobutene-emitting enrichment cultures obtained from two treatment ponds operating at Leuna, Germany. The possible use of alkene formation as an easy-to-measure indicator of aerobic fuel oxygenate biodegradation in contaminated aquifers is discussed.The extensive use of methyl tert-butyl ether (MTBE) and related compounds as fuel oxygenates has resulted in contamination of numerous groundwater sites in the United States and Europe (13,26,33,51). Although MTBE is now banned in some countries and may be phased out in others (52), it will persist at polluted sites for a long time due to its poor biodegradability. Despite this enormous environmental prevalence, only a few strains capable of growth on MTBE, ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME) have been found, and fuel oxygenate metabolism has not been elucidated in full detail (20,30,31,46). Since the pioneering works of Salanitro et al. and Steffan et al. (42,43,48), it is generally agreed that aerobic MTBE degradation proceeds via a monooxygenase-catalyzed ether cleavage resulting in formation of tert-butyl alcohol (TBA). The latter is hydroxylated to the corresponding diol, 2-methyl-1,2-propanediol (MPD), which is further oxidized to 2-hydroxyisobutyric acid (2-HIBA). This branched carboxylic acid is then introduced into common metabolic routes after isomerization to 3-hydroxybutyric acid (39). Since ETBE shares the tert-butyl structure with MTBE, it should have a similar degradation path via TBA (8, 30). The biochemistry of TAME catabol...

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Section: Discussionmentioning

confidence: 99%

Formation of Alkenes via Degradation of tert -Alkyl Ethers and Alcohols by Aquincola tertiaricarbonis L108 and Methylibium spp

Schäfer

Muzica

Schuster

et al. 2011

Appl Environ Microbiol

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“…A second disadvantage of isotope approaches relates to the fact that these analyses do not demonstrate the activity of specific biodegradation processes at the time of sampling (Kuder and Philp 2008 ). Furthermore, hydrogen isotopes in alcohol molecules are often easily exchangeable with hydrogen isotopes from water.…”

Section: Isotopic Methods To Assess Anaerobic Biodegradation Of Etbe ...mentioning

confidence: 99%

Potential of stable isotope analysis to deduce anaerobic biodegradation of ethyl tert-butyl ether (ETBE) and tert-butyl alcohol (TBA) in groundwater: a review

van der Waals,

Thornton,

Rolfe

et al. 2024

Environ Sci Pollut Res

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Understanding anaerobic biodegradation of ether oxygenates beyond MTBE in groundwater is important, given that it is replaced by ETBE as a gasoline additive in several regions. The lack of studies demonstrating anaerobic biodegradation of ETBE, and its product TBA, reflects the relative resistance of ethers and alcohols with a tertiary carbon atom to enzymatic attack under anoxic conditions. Anaerobic ETBE- or TBA-degrading microorganisms have not been characterized. Only one field study suggested anaerobic ETBE biodegradation. Anaerobic (co)metabolism of ETBE or TBA was reported in anoxic microcosms, indicating their biodegradation potential in anoxic groundwater systems. Non-isotopic methods, such as the detection of contaminant loss, metabolites, or ETBE- and TBA-degrading bacteria are not sufficiently sensitive to track anaerobic biodegradation in situ. Compound- and position-specific stable isotope analysis provides a means to study MTBE biodegradation, but isotopic fractionation of ETBE has only been studied with a few aerobic bacteria (εC −0.7 to −1.7‰, εH −11 to −73‰) and at one anoxic field site (δ2H-ETBE +14‰). Similarly, stable carbon isotope enrichment (δ13C-TBA +6.5‰) indicated TBA biodegradation at an anoxic field site. CSIA and PSIA are promising methods to detect anaerobic ETBE and TBA biodegradation but need to be investigated further to assess their full potential at field scale. Graphical abstract

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“…Although MBTs focusing on anaerobic degradation of chlorinated solvents remain the most widely-applied, MBTs are available for documenting a variety of attenuation processes for many other contaminants. Methods that focus on petroleum hydrocarbons 100 , fuel oxygenates such as MTBE 57,101 , energetics 102,103 , and perchlorate 104,105 have been established. Identifying and quantifying biomarkers of aerobic degradation of chlorinated solvents has been a goal of several studies (e.g., 106,107) and the development of these tools has relevance for documenting natural attenuation potential in large dilute plumes that are often dominated by aerobic zones (see on-going ESTCP project 108 ).…”

Section: How Can Molecular Biological Tools Help Me With Mna? (Page 4)mentioning

confidence: 99%

Frequently Asked Questions about Monitored Natural Attenuation in Groundwater

Adamson¹,

Newell²

2014

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Modern geochemical and molecular tools for monitoring in-situ biodegradation of MTBE and TBA

Cited by 9 publications

References 69 publications

Formation of Alkenes via Degradation of tert -Alkyl Ethers and Alcohols by Aquincola tertiaricarbonis L108 and Methylibium spp

Formation of Alkenes via Degradation of tert -Alkyl Ethers and Alcohols by Aquincola tertiaricarbonis L108 and Methylibium spp

Potential of stable isotope analysis to deduce anaerobic biodegradation of ethyl tert-butyl ether (ETBE) and tert-butyl alcohol (TBA) in groundwater: a review

Frequently Asked Questions about Monitored Natural Attenuation in Groundwater

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