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Elsey JL, Miller EL, Christ JA, Abriola LM. On the reliable estimation of sequential Monod kinetic parameters. JOURNAL OF CONTAMINANT HYDROLOGY 2024; 262:104323. [PMID: 38430692 DOI: 10.1016/j.jconhyd.2024.104323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 02/15/2024] [Accepted: 02/19/2024] [Indexed: 03/05/2024]
Abstract
While dozens of studies have attempted to estimate the Monod kinetic parameters of microbial reductive dechlorination, published values in the literature vary by 2-6 orders of magnitude. This lack of consensus can be attributed in part to limitations of both experimental design and parameter estimation techniques. To address these issues, Hamiltonian Monte Carlo was used to produce more than one million sets of realistic simulated microcosm data under a variety of experimental conditions. These data were then employed in model fitting experiments using a number of parameter estimation algorithms for determining Monod kinetic parameters. Analysis of data from conventional triplicate microcosms yielded parameter estimates characterized by high collinearity, resulting in poor estimation accuracy and precision. Additionally, confidence intervals computed by commonly used classical regression analysis techniques contained true parameter values much less frequently than their nominal confidence levels. Use of an alternative experimental design, requiring the same number of analyses as conventional experiments but comprised of microcosms with varying initial chlorinated ethene concentrations, is shown to result in order-of-magnitude decreases in parameter uncertainty. A Metropolis algorithm which can be run on a typical personal computer is demonstrated to return more reliable parameter interval estimates.
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Affiliation(s)
- Jack L Elsey
- Department of Civil and Environmental Engineering, Tufts University, Medford, MA 02155, USA
| | - Eric L Miller
- Department of Electrical and Computer Engineering, Tufts University, Medford, MA 02155, USA
| | | | - Linda M Abriola
- School of Engineering, Brown University, Providence, RI 02912, USA.
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2
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Elsey JL, Christ JA, Abriola LM. Quantifying Impacts of Microcosm Mass Loss on Kinetic Constant Estimation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:13822-13833. [PMID: 34618436 DOI: 10.1021/acs.est.1c03452] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Microcosm experiments to assess microbial reductive dechlorination of chlorinated aliphatic hydrocarbons typically experience 5-50% mass loss due to frequent sampling events and diffusion through septa. A literature review, however, reveals that models fit to such experiments for kinetic constant estimation have generally failed to account for experimental mass loss. To investigate possible resultant bias in best-fit parameters, a series of numerical experiments was conducted in which Monod kinetic models with and without mass loss were fit to more than 1300 synthetic data sets, generated using published microcosm data. Models that failed to account for mass loss resulted in significant fitted parameter bias. Bias ranged from 5 to 45% of the parameter magnitude for Monte Carlo simulations with low (approximately 10%) mass loss to 20-120% for simulations with high (approximately 40%) mass loss. In addition, for high mass loss simulations, best-fit values consistently fell along the bounds of the optimization range. These results suggest that failure to properly account for mass loss in microcosms may lead to inaccurate estimation of kinetic constants and may explain some of the literature-reported variability in these parameters. A model is presented that provides a method for including sampling and diffusional mass losses to improve kinetic constant estimation accuracy.
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Affiliation(s)
- Jack L Elsey
- Department of Civil and Environmental Engineering, Tufts University, Medford, Massachusetts 02155, United States
| | - John A Christ
- S&B Christ Consulting, Las Vegas, Nevada 89134, United States
| | - Linda M Abriola
- School of Engineering, Brown University, Providence, Rhode Island 02912, United States
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3
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Matturro B, Majone M, Aulenta F, Rossetti S. Correlations between maximum reductive dechlorination rates and specific biomass parameters in Dehalococcoides mccartyi consortia enriched on chloroethenes PCE, TCE and cis-1,2-DCE. FEMS Microbiol Ecol 2021; 97:6253249. [PMID: 33899920 DOI: 10.1093/femsec/fiab064] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 04/23/2021] [Indexed: 01/04/2023] Open
Abstract
One of the challenges to implementing the modeling of the biological reductive dechlorination (RD) process is the evaluation of biological parameters that represent the abundance/activity levels of the microorganisms involved in the biodegradation of chloroethenes. Here we report a combined analysis of kinetic and specific biomass parameters conducted on three dechlorinating consortia enriched on PCE, TCE and cis-1,2-DCE. In these consortia, Dehalococcoides mccartyi (Dhc) represented ≥70% of the bacterial population identified via 16S rRNA gene amplicon sequencing. Quantitative biomolecular methods were used to generate specific biomass parameters targeting either the Dhc population (16S rRNA genes or cells) or specific genes encoding RD process-involved reductive dehalogenases. The correlation factor between the abundance of active Dhc cells or tceA gene copies and maximum RD rates allowed to predict an increment of 7E+09 of active Dhc cells or 5E+09 tceA gene copies/L under controlled conditions. Diversely, the utilization of gene transcripts as biomass parameters for RD modeling did not provide reliable correlations with kinetic performances. This study provides valuable insights for further modeling of the RD process through the utilization of specific biomass parameters.
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Affiliation(s)
- B Matturro
- Water Research Institute, IRSA-CNR, Via Salaria km 29.300, Monterotondo (RM) 00015, Italy
| | - M Majone
- Department of Chemistry, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - F Aulenta
- Water Research Institute, IRSA-CNR, Via Salaria km 29.300, Monterotondo (RM) 00015, Italy
| | - S Rossetti
- Water Research Institute, IRSA-CNR, Via Salaria km 29.300, Monterotondo (RM) 00015, Italy
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4
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Waseem H, Ali J, Syed JH, Jones KC. Establishing the relationship between molecular biomarkers and biotransformation rates: Extension of knowledge for dechlorination of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs). ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 263:114676. [PMID: 33618452 DOI: 10.1016/j.envpol.2020.114676] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 04/20/2020] [Accepted: 04/24/2020] [Indexed: 06/12/2023]
Abstract
Anaerobic reductive treatment technologies offer cost-effective and large-scale treatment of chlorinated compounds, including polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs). The information about the degradation rates of these compounds in natural settings is critical but difficult to obtain because of slow degradation processes. Establishing a relationship between biotransformation rate and abundance of biomarkers is one of the most critical challenges faced by the bioremediation industry. When solved for a given contaminant, it may result in significant cost savings because of serving as a basis for action. In the current review, we have summarized the studies highlighting the use of biomarkers, particularly DNA and RNA, as a proxy for reductive dechlorination of chlorinated ethenes. As the use of biomarkers for predicting biotransformation rates has not yet been executed for PCDD/Fs, we propose the extension of the same knowledge for dioxins, where slow degradation rates further necessitate the need for developing the biomarker-rate relationship. For this, we have first retrieved and calculated the bioremediation rates of different PCDD/Fs and then highlighted the key sequences that can be used as potential biomarkers. We have also discussed the implications and hurdles in developing such a relationship. Improvements in current techniques and collaboration with some other fields, such as biokinetic modeling, can improve the predictive capability of the biomarkers so that they can be used for effectively predicting biotransformation rates of dioxins and related compounds. In the future, a valid and established relationship between biomarkers and biotransformation rates of dioxin may result in significant cost savings, whilst also serving as a basis for action.
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Affiliation(s)
- Hassan Waseem
- Department of Civil & Environmental Engineering, Michigan State University, East Lansing, MI, 48823, USA; Department of Biotechnology, University of Sialkot, Sialkot, Punjab 51310, Pakistan
| | - Jafar Ali
- Key Laboratory of Environmental Nanotechnology and Health Effects, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Beijing, 100085, China
| | - Jabir Hussain Syed
- Department of Meteorology, COMSATS University, Tarlai Kalan Park Road, Islamabad, 45550, Pakistan.
| | - Kevin C Jones
- Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK
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5
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Yin Y, Yan J, Chen G, Murdoch FK, Pfisterer N, Löffler FE. Nitrous Oxide Is a Potent Inhibitor of Bacterial Reductive Dechlorination. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:692-701. [PMID: 30558413 PMCID: PMC6944068 DOI: 10.1021/acs.est.8b05871] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Organohalide-respiring bacteria are key players for the turnover of organohalogens. At sites impacted with chlorinated ethenes, bioremediation promotes reductive dechlorination; however, stoichiometric conversion to environmentally benign ethene is not always achieved. We demonstrate that nitrous oxide (N2O), a compound commonly present in groundwater, inhibits organohalide respiration. N2O concentrations in the low micromolar range decreased dechlorination rates and resulted in incomplete dechlorination of tetrachloroethene (PCE) in Geobacter lovleyi strain SZ and of cis-1,2-dichloroethene ( cDCE) and vinyl chloride (VC) in Dehalococcoides mccartyi strain BAV1 axenic cultures. Presumably, N2O interferes with reductive dechlorination by reacting with super-reduced Co(I)-corrinoids of reductive dehalogenases, which is supported by the finding that N2O did not inhibit corrinoid-independent fumarate-to-succinate reduction in strain SZ. Kinetic analyses revealed a best fit to the noncompetitive Michaelis-Menten inhibition model and determined N2O inhibitory constants, KI, for PCE and cDCE dechlorination of 40.8 ± 3.8 and 21.2 ± 3.5 μM in strain SZ and strain BAV1, respectively. The lowest KI value of 9.6 ± 0.4 μM was determined for VC to ethene reductive dechlorination in strain BAV1, suggesting that this crucial dechlorination step for achieving detoxification is most susceptible to N2O inhibition. Groundwater N2O concentrations exceeding 100 μM are not uncommon, especially in watersheds impacted by nitrate runoff from agricultural sources. Thus, dissolved N2O measurements can inform about cDCE and VC stalls at sites impacted with chlorinated ethenes.
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Affiliation(s)
- Yongchao Yin
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Jun Yan
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Liaoning 110016, People’s Republic of China
| | - Gao Chen
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Fadime Kara Murdoch
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Nina Pfisterer
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Frank E. Löffler
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States
- Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, Tennessee 37996, United States
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Corresponding Author: Phone: (865) 974-4933.
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6
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Phelan TJ, Abriola LM, Gibson JL, Smits KM, Christ JA. Development and application of a screening model for evaluating bioenhanced dissolution in DNAPL source zones. JOURNAL OF CONTAMINANT HYDROLOGY 2015; 183:1-15. [PMID: 26484479 DOI: 10.1016/j.jconhyd.2015.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 10/03/2015] [Accepted: 10/03/2015] [Indexed: 06/05/2023]
Abstract
In-situ bioremediation, a widely applied treatment technology for source zones contaminated with dense non-aqueous phase liquids (DNAPLs), has proven economical and reasonably efficient for long-term management of contaminated sites. Successful application of this remedial technology, however, requires an understanding of the complex interaction of transport, mass transfer, and biotransformation processes. The bioenhancement factor, which represents the ratio of DNAPL mass transfer under microbially active conditions to that which would occur under abiotic conditions, is commonly used to quantify the effectiveness of a particular bioremediation remedy. To date, little research has been directed towards the development and validation of methods to predict bioenhancement factors under conditions representative of real sites. This work extends an existing, first-order, bioenhancement factor expression to systems with zero-order and Monod kinetics, representative of many source-zone scenarios. The utility of this model for predicting the bioenhancement factor for previously published laboratory and field experiments is evaluated. This evaluation demonstrates the applicability of these simple bioenhancement factors for preliminary experimental design and analysis, and for assessment of dissolution enhancement in ganglia-contaminated source zones. For ease of application, a set of nomographs is presented that graphically depicts the dependence of bioenhancement factor on physicochemical properties. Application of these nomographs is illustrated using data from a well-documented field site. Results suggest that this approach can successfully capture field-scale, as well as column-scale, behavior. Sensitivity analyses reveal that bioenhanced dissolution will critically depend on in-situ biomass concentrations.
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Affiliation(s)
- Thomas J Phelan
- United States Air Force Academy, Department of Civil & Environmental Engineering, 2354 Fairchild Dr. STE 6J-159, USAF Academy, CO 80840-6208, United States.
| | - Linda M Abriola
- Tufts University, School of Engineering, 105 Anderson Hall, 200 College Ave., Medford, MA 02155-5530, United States.
| | - Jenny L Gibson
- Headquarters United States Air Force, Directorate of Civil Engineers, 1260 Air Force Pentagon, Washington, DC 20330-1030, United States.
| | - Kathleen M Smits
- Colorado School of Mines, Department of Civil & Environmental Engineering, 1500 Illinois St., Golden, CO 80401-1887, United States.
| | - John A Christ
- United States Air Force Academy, Department of Civil & Environmental Engineering, 2354 Fairchild Dr. STE 6J-159, USAF Academy, CO 80840-6208, United States.
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7
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Hiortdahl KM, Borden RC. Enhanced reductive dechlorination of tetrachloroethene dense nonaqueous phase liquid with EVO and Mg(OH)2. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 48:624-631. [PMID: 24328264 DOI: 10.1021/es4042379] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In situ treatment of dense nonaqueous phase liquids (DNAPL) by enhanced reductive dechlorination (ERD) can be limited by contaminant toxicity, low pH, and challenges in effectively delivering electron donor. Flushing emulsified vegetable oil (EVO), colloidal Mg(OH)2 buffer, and a bioaugmentation culture (BC) through a zone containing neat tetrachloroethene (PCE) was effective in reducing contaminant toxicity, limiting pH declines, and accelerating bioenhanced dissolution of the DNAPL. In the effluent of porous media columns with little fine material, PCE concentrations reached a maximum of 40-50 times PCE aqueous solubility in water, demonstrating NAPL PCE was distributed throughout the 1.5 m column length. In a column treated with only EVO+BC, reductive dechlorination was limited. However, a single injection of EVO+Mg(OH)2+BC was effective in reducing PCE to below detection for over 400 days with a large increase in Cl(-) and dichloroethene (DCE), accelerating bioenhanced DNAPL dissolution. Dechlorination rates gradually increased over time with the rate of total ethene (TE) release from the Mg(OH)2+EVO+BC column reaching 5-6 times the TE release rate from the EVO+BC column. The accelerated dechlorination was likely due to both Mg(OH)2 addition which limited pH declines from HCl, volatile fatty acids (VFAs), and inorganic carbon (IC) production, and formation of a mixed PCE-vegetable oil NAPL which provided a readily accessible electron donor, resulting in rapid PCE degradation with reduced PCE toxicity.
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Affiliation(s)
- Kirsten M Hiortdahl
- Department of Civil, Construction and Environmental Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States
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8
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Huang D, Lai Y, Becker JG. Impact of initial conditions on extant microbial kinetic parameter estimates: application to chlorinated ethene dehalorespiration. Appl Microbiol Biotechnol 2013; 98:2279-88. [PMID: 23963272 DOI: 10.1007/s00253-013-5171-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Revised: 08/01/2013] [Accepted: 08/02/2013] [Indexed: 11/27/2022]
Abstract
Monod kinetics are the foundation of mathematical models of many environmentally important biological processes, including the dehalorespiration of chlorinated ethene groundwater contaminants. The Monod parameters--qmax, the maximum specific substrate utilization rate, and KS, the half-saturation constant--are typically estimated in batch assays, which are superficially simple to prepare and maintain. However, if initial conditions in batch assays are not chosen carefully, it is unlikely that the estimated parameter values will be meaningful because they do not reflect microbial activity in the environmental system of interest, and/or they are not mathematically identifiable. The estimation of qmax and KS values that are highly correlated undoubtedly contributes significantly to the wide range in reported parameter values and may undermine efforts to use mathematical models to demonstrate the occurrence of natural attenuation or predict the performance of engineered bioremediation approaches. In this study, a series of experimental and theoretical batch kinetic assays were conducted using the tetrachloroethene-respirer Desulfuromonas michiganensis to systematically evaluate the effects of initial batch assay conditions, expressed as the initial substrate (S0)-to-initial biomass concentration (X0) ratio (S0/X0) and the S0/KS ratio on parameter correlation. An iterative approach to obtain meaningful Monod parameter estimates was developed and validated using three different strains and can be broadly applied to a range of other substrates and populations. While the S0/X0 ratio is critical to obtaining kinetic parameter estimates that reflect in situ microbial activity, this study shows that optimization of the S0/KS ratio is key to minimizing Monod parameter correlation.
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Bælum J, Chambon JC, Scheutz C, Binning PJ, Laier T, Bjerg PL, Jacobsen CS. A conceptual model linking functional gene expression and reductive dechlorination rates of chlorinated ethenes in clay rich groundwater sediment. WATER RESEARCH 2013; 47:2467-78. [PMID: 23490098 DOI: 10.1016/j.watres.2013.02.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 02/06/2013] [Accepted: 02/08/2013] [Indexed: 05/26/2023]
Abstract
We used current knowledge of cellular processes involved in reductive dechlorination to develop a conceptual model to describe the regulatory system of dechlorination at the cell level; the model links bacterial growth and substrate consumption to the abundance of messenger RNA of functional genes involved in the dechlorination process. The applicability of the model was tested on a treatability study of biostimulated and bioaugmented microcosms. Using quantitative real time PCR, high-resolution expression profiles of the functional reductive dehalogenase genes bvcA and vcrA were obtained during two consecutive dechlorination events of trichlorethene, cis-dichlorethene and vinyl chloride. Up-regulation of the bvcA (for the biostimulated microcosms) and vcrA (for the bioaugmented microcosms) gene expression fitted well with high rates of dechlorination of vinyl chloride, while no known transcripts could be measured during trichloroethene and cis-dichlorethene dechlorination. Maximum concentrations of 2.1 and 1.7 transcripts per gene of the bvcA and vcrA genes, respectively, were measured at the same time points as maximum dechlorination rates were observed. The developed model compared well with the experimental data for both biostimulated and bioaugmented microcosms under non-steady state conditions and was supported by results from a recently published study under steady state conditions.
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Affiliation(s)
- Jacob Bælum
- The Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen, Denmark
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10
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Heavner GLW, Rowe AR, Mansfeldt CB, Pan JK, Gossett JM, Richardson RE. Molecular biomarker-based biokinetic modeling of a PCE-dechlorinating and methanogenic mixed culture. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:3724-33. [PMID: 23363057 DOI: 10.1021/es303517s] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Bioremediation of chlorinated ethenes via anaerobic reductive dechlorination relies upon the activity of specific microbial populations--most notably Dehalococcoides (DHC) strains. In the lab and field Dehalococcoides grow most robustly in mixed communities which usually contain both fermenters and methanogens. Recently, researchers have been developing quantitative molecular biomarkers to aid in field site diagnostics and it is hoped that these biomarkers could aid in the modeling of anaerobic reductive dechlorination. A comprehensive biokinetic model of a community containing Dehalococcoides mccartyi (formerly D. ethenogenes) was updated to describe continuously fed reactors with specific biomass levels based on quantitative PCR (qPCR)-based population data (DNA and RNA). The model was calibrated and validated with subsets of chemical and molecular biological data from various continuous feed experiments (n = 24) with different loading rates of the electron acceptor (1.5 to 482 μeeq/L-h), types of electron acceptor (PCE, TCE, cis-DCE) and electron donor to electron acceptor ratios. The resulting model predicted the sum of dechlorination products vinyl chloride (VC) and ethene (ETH) well. However, VC alone was under-predicted and ETH was over predicted. Consequently, competitive inhibition among chlorinated ethenes was examined and then added to the model. Additionally, as 16S rRNA gene copy numbers did not provide accurate model fits in all cases, we examined whether an improved fit could be obtained if mRNA levels for key functional enzymes could be used to infer respiration rates. The resulting empirically derived mRNA "adjustment factors" were added to the model for both DHC and the main methanogen in the culture (a Methanosaeta species) to provide a more nuanced prediction of activity. Results of this study suggest that at higher feeding rates competitive inhibition is important and mRNA provides a more accurate indicator of a population's instantaneous activity than 16S rRNA gene copies alone as biomass estimates.
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Affiliation(s)
- Gretchen L W Heavner
- School of Civil and Environmental Engineering, Cornell University, Ithaca, NY, USA
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11
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Lai Y, Becker JG. Compounded effects of chlorinated ethene inhibition on ecological interactions and population abundance in a Dehalococcoides - Dehalobacter coculture. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:1518-25. [PMID: 23281935 DOI: 10.1021/es3034582] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The development of rational and effective engineered bioremediation approaches for sites contaminated with chlorinated solvents requires a fundamental understanding of the factors limiting the in situ activity of dehalorespiring bacteria. Frequently, multiple dehalorespiring bacteria are present at contaminated sites, particularly when bioaugmentation is applied. The ecological interactions between different dehalorespiring populations can-along with hydrodynamic and other environmental factors-affect their activity and thus the rates and extent of dehalorespiration. An integrated experimental and modeling approach was used to evaluate the ecological interactions between two hydrogenotrophic, dehalorespiring strains. A dual Monod model of dehalorespiration provided a good fit to the chlorinated ethene concentrations measured in a coculture of Dehalococcoides mccartyi 195 and Dehalobacter restrictus growing on tetrachloroethene (PCE) and excess H(2) in a continuous-flow reactor. Inhibition of dehalorespiration by chlorinated ethenes was previously observed in cultures containing Dehalococcoides or Dehalobacter strains. Therefore, inhibition coefficients were estimated for Dhc. mccartyi 195 and Dhb. restrictus. The inhibition effects of PCE and TCE on VC dechlorination by Dhc. mccartyi 195, and of VC on PCE and TCE dechlorination by Dhb. restrictus, were compounded when these strains were grown in coculture, and dehalorespiring population abundance and survival could be accurately predicted only by incorporating these complex interactions into the dual Monod model.
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Affiliation(s)
- Yenjung Lai
- Swette Center for Environmental Biotechnology, The Biodesign Institute at Arizona State University, Tempe, Arizona 85287-5701, United States
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12
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Chambon JC, Bjerg PL, Scheutz C, Baelum J, Jakobsen R, Binning PJ. Review of reactive kinetic models describing reductive dechlorination of chlorinated ethenes in soil and groundwater. Biotechnol Bioeng 2012; 110:1-23. [DOI: 10.1002/bit.24714] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Revised: 08/13/2012] [Accepted: 08/16/2012] [Indexed: 11/08/2022]
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13
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Braeckevelt M, Seeger EM, Paschke H, Kuschk P, Kaestner M. Adaptation of a constructed wetland to simultaneous treatment of monochlorobenzene and perchloroethene. INTERNATIONAL JOURNAL OF PHYTOREMEDIATION 2011; 13:998-1013. [PMID: 21972567 DOI: 10.1080/15226514.2010.549860] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Mixed groundwater contaminations by chlorinated volatile organic compounds (VOC) cause environmental hazards if contaminated groundwater discharges into surface waters and river floodplains. Constructed wetlands (CW) or engineered natural wetlands provide a promising technology for the protection of sensitive water bodies. We adapted a constructed wetland able to treat monochlorobenzene (MCB) contaminated groundwater to a mixture of MCB and tetrachloroethene (PCE), representing low and high chlorinated model VOC. Simultaneous treatment of both compounds was efficient after an adaptation time of 2 1/2 years. Removal of MCB was temporarily impaired by PCE addition, but after adaptation a MCB concentration decrease of up to 64% (55.3 micromol L(-1)) was observed. Oxygen availability in the rhizosphere was relatively low, leading to sub-optimal MCB elimination but providing also appropriate conditions for PCE dechlorination. PCE and metabolites concentration patterns indicated a very slow system adaptation. However, under steady state conditions complete removal of PCE inflow concentrations of 10-15 micromol L(-1) was achieved with negligible concentrations of chlorinated metabolites in the outflow. Recovery of total dechlorination metabolite loads corresponding to 100%, and ethene loads corresponding to 30% of the PCE inflow load provided evidence for complete reductive dechlorination, corroborated by the detection of Dehalococcoides sp.
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Affiliation(s)
- M Braeckevelt
- Department of Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany.
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14
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Huang D, Becker JG. Dehalorespiration model that incorporates the self-inhibition and biomass inactivation effects of high tetrachloroethene concentrations. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2011; 45:1093-1099. [PMID: 21182287 DOI: 10.1021/es102729v] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In the vicinity of dense nonaqueous phase liquid (DNAPL) contaminant source zones, aqueous concentrations of tetrachloroethene (PCE) in groundwater may approach saturation levels. In this study, the ability of two PCE-respiring strains (Desulfuromonas michiganensis and Desulfitobacterium strain PCE1) to dechlorinate high concentrations of PCE was experimentally evaluated and depended on the initial biomass concentration. This suggests high PCE concentrations permanently inactivated a fraction of biomass, which, if sufficiently large, prevented dechlorination from proceeding. The toxic effects of PCE were incorporated into a model of dehalorespirer growth by adapting the transformation capacity concept previously applied to describe biomass inactivation by products of cometabolic TCE oxidation. The inactivation growth model was coupled to the Andrews substrate utilization model, which accounts for the self-inhibitory effects of PCE on dechlorination rates, and fit to the experimental data. The importance of incorporating biomass inactivation and self-inhibition effects when modeling reductive dechlorination of high PCE concentrations was demonstrated by comparing the goodness-of-fit of the Andrews biomass inactivation and three alternate models that do capture these factors. The new dehalorespiration model should improve our ability to predict contaminant removal in DNAPL source zones and determine the inoculum size needed to successfully implement bioaugmentation of DNAPL source zones.
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Affiliation(s)
- Deyang Huang
- University of Maryland, College Park, Maryland 20742, United States
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