Grantee Research Project Results
2003 Progress Report: Microbial Transformation of Fluorinated Environmental Pollutants
EPA Grant Number: R830249Title: Microbial Transformation of Fluorinated Environmental Pollutants
Investigators: Loeffler, Frank E. , Sohn, Rosa , Song, Ryoung
Institution: Georgia Institute of Technology
EPA Project Officer: Aja, Hayley
Project Period: September 1, 2002 through August 31, 2004 (Extended to August 31, 2005)
Project Period Covered by this Report: September 1, 2002 through August 31, 2003
Project Amount: $198,936
RFA: Futures Research in Natural Sciences (2001) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Land and Waste Management , Hazardous Waste/Remediation
Objective:
The objectives of this research project are to: (1) demonstrate that fluorinated organic compounds (FOCs) can serve as terminal electron acceptors in anaerobic environments; (2) use model compounds to learn more about the microbial strategies to degrade fluorinated hydrocarbons; and (3) demonstrate that environmentally relevant polyfluorinated and perfluorinated hydrocarbons can undergo microbially mediated defluorination/transformation reactions. FOCs have been extensively manufactured and used for the past several decades as surfactants, pesticides formulations, lubricants, refrigerants, fire retardants, drugs, cosmetics, paints, adhesives, etc. Recent studies indicated that FOCs are not biologically inert, exhibit toxic effects on humans and animals, and impact overall ecosystem health. This research effort explores the microbial degradation of fluorinated model compounds and environmentally relevant FOCs to improve our understanding of the fate of these chemicals in the natural environment.
Progress Summary:
Dehalogenation of Chlorofluorohydrocarbons by Chlororespiring Pure Cultures
To explore reductive defluorination, chlororespiring cultures (i.e., cultures that couple growth with reductive dechlorination of chlorinated ethenes) were challenged with fluorinated hydrocarbons. The growth of three dechlorinating pure cultures (i.e., Desulfuromonas michiganensis strain BB1, Sulfurospirillum multivorans, and Geobacter sp. strain SZ) was tested with 1,1-dichloro-2,2-difluoroethene. All cultures rapidly produced 2-chloro-1,1-difluoroethene, and 1,1-difluoroethene accumulated in cultures of S. multivorans. The formation of both transformation products was confirmed by gas chromatography/mass spectrometry analyses. No further transformation was observed, and no fluoride release occurred. Reductive dechlorination also occurred in cultures amended with cis- and trans-1,2-dichloro-1,2-difluoroethene or chlorotrifluoroethene, but no fluoride release occurred. Trichlorofluoroethene rapidly was transformed to one major product that has not yet been identified. No dehalogenation was observed in cultures of Dehalococcoides sp. strain FL2 nor Dehalococcoides sp. strain BAV1, suggesting that these populations cannot transform these chlorofluorohydrocarbons.
Microcosms and Enrichment Efforts
To date, microcosms have been established with soil, sediment, and aquifer materials collected from eight different sites to test for the transformation of trifluoroacetate (TFA), difluoroacetate, monofluoroacetate (MFA), 4-nitro-3-trifluoromethyl phenol (TFM), ethyl-4,4,4-trifluoroacetoacetate, and fluorinated benzoates under aerobic and anaerobic conditions. Disappearance of the fluorinated target compound has been observed in numerous microcosms, and current efforts focus on identifying transformation products, including fluoride release, and establishing enrichment cultures. The focus is on microcosms and cultures that show removal of TFA because this compound is constantly being introduced into the environment in increasing concentrations, and its fate is poorly understood.
Aerobic Degradation of Fluorinated Alkanes
Little is known about the fate of medium chain length fluorinated alkanes. Poly- and perfluorinated medium chain length fluorinated hydrocarbons are of particular concern because of their widespread release into the environment. To elucidate the microbial strategies that transform such FOCs, 1-fluorodecane (1-FD) was chosen as a model compound, and the degradation of this compound was studied with Pseudomonas sp. strain 273. Strain 273 grew with 1-FD as the sole source of carbon and energy, and stoichiometric amounts of fluoride were released into the growth medium (see Figure 1). No intermediates, such as MFA, were detected during growth with 1-FD.
Figure 1. Microbial Degradation of 1-FD by Pseudomonas sp. Strain 273
Strain 273 readily grew with acetate as the sole source of carbon and energy, but failed to grow with MFA. When the organism was grown with a mixture of acetate and MFA, growth occurred and acetate was consumed, but MFA was not degraded. Apparently, MFA had no inhibitory effect on growth of strain 273 with acetate. Strain 273 metabolizes even-chain length alkanes via ß-oxidation, suggesting that MFA is an intermediate in the degradation of 1-FD. Interestingly, MFA was readily degraded in cultures that were amended with 1-FD, and stoichiometric amounts of fluoride were released. This observation is relevant and emphasizes that the complex interaction between microbes and their substrates must be understood before meaningful and reliable predictions on the fate of FOCs in the natural environment are possible.
Future Activities:
Future activities will take place following the completion of our studies that explore the ability of chlororespiring pure culture to dehalogenate chlorofluorohydrocarbons. We will study defluorination in chlorinated solvent dechlorinating mixed cultures that we have available. We will continue our efforts with microcosms and enrichment cultures to explore the fate of environmentally relevant FOCs, including TFA.
We will continue our efforts to elucidate fluoroalkane degradation with strain 273. We will expand our investigations and explore compounds that contain a trifluoromethyl group. For instance, we will study the growth of strain 273 with TFA and 4,4,4-trifluorobutyrate in the presence and absence of 1-FD or decane.
Journal Articles:
No journal articles submitted with this report: View all 6 publications for this projectSupplemental Keywords:
fluorinated hydrocarbons, sediments, human and ecosystem health, biodegradation, detoxification, restoration, halorespiration, defluorination, halogenated hydrocarbons., RFA, Scientific Discipline, Water, Ecosystem Protection/Environmental Exposure & Risk, Environmental Chemistry, Restoration, Environmental Monitoring, Aquatic Ecosystem Restoration, Futures, Exp. Research/future, biodiversity, biodegradation, defluorination, conservation, contaminant uptake, ecological pollutants, exploratory research, environmental rehabilitation, environmental stress, ecotoxicologyProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.