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Martin Thullner - One of the best experts on this subject based on the ideXlab platform.
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quantification of organic Pollutant Degradation in contaminated aquifers using compound specific stable isotope analysis review of recent developments
Organic Geochemistry, 2012Co-Authors: Martin Thullner, Florian Centler, Hanshermann Richnow, Anko FischerAbstract:Abstract Compound specific stable isotope analysis (CSIA) has been established as a viable tool for proving, characterizing and assessing Degradation of organic Pollutants within contaminated aquifers. The fractionation of stable isotopes during contaminant Degradation leads to observable shifts in stable isotope ratios which can serve as an indicator for in situ Pollutant Degradation and allow for a quantitative assessment by means of the so-called Rayleigh (distillation) equation. This review highlights the recent developments of the Rayleigh equation approach for quantifying in situ Degradation of organic Pollutants in contaminated aquifers. The advantages and limitations of the Rayleigh equation approach are discussed and suggestions for improvements are given. Concepts are provided to estimate the uncertainty due to errors or variability of input parameters and how to deal with such uncertainty. Moreover, the applicability of the Rayleigh equation approach is evaluated regarding the heterogeneity and complexity of groundwater systems. For such systems, the review discusses the relevance of non-destructive processes, which affect the concentration (e.g., dispersive mixing) and potentially also the stable isotope ratio of contaminants (e.g., sorption, volatilization), and the resulting implications for the Rayleigh equation approach.
Jeremy D Semrau - One of the best experts on this subject based on the ideXlab platform.
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priority Pollutant Degradation by the facultative methanotroph methylocystis strain sb2
Applied Microbiology and Biotechnology, 2013Co-Authors: Sheeja Jagadevan, Jeremy D SemrauAbstract:Methylocystis strain SB2, a facultative methanotroph capable of growth on multi-carbon compounds, was screened for its ability to degrade the priority Pollutants 1,2-dichloroethane (1,2-DCA), 1,1,2-trichloroethane (1,1,2-TCA), and 1,1-dichloroethylene (1,1-DCE), as well as cis-dichloroethylene (cis-DCE) when grown on methane or ethanol. Methylocystis strain SB2 degraded 1,2-DCA and 1,1,2-TCA when grown on either substrate and cis-DCE when grown on methane. Growth of Methylocystis strain SB2 on methane was inhibited in the presence of all compounds, while only 1,1-DCE and cis-DCE inhibited growth on ethanol. No Degradation of any chlorinated hydrocarbon was observed in ethanol-grown cultures when particulate methane monooxygenase (pMMO) activity was inhibited with the addition of acetylene, indicating that competition for binding to the pMMO between the chlorinated hydrocarbons and methane limited both methanotrophic growth and Pollutant Degradation when this strain was grown on methane. Characterization of Methylocystis strain SB2 found no evidence of a high-affinity form of pMMO for methane, nor could this strain utilize 1,2-DCA or its putative oxidative products 2-chloroethanol or chloroactetic acid as sole growth substrates, suggesting that this strain lacks appropriate dehydrogenases for the conversion of 1,2-DCA to glyoxylate. As ethanol: (1) can be used as an alternative growth substrate for promoting Pollutant Degradation by Methylocystis strain SB2 as the pMMO is not required for its growth on ethanol and (2) has been used to enhance the mobility of chlorinated hydrocarbons in situ, it is proposed that ethanol can be used to enhance both Pollutant transport and bioDegradation by Methylocystis strain SB2.
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Pollutant Degradation by a Methylocystis strain SB2 grown on ethanol: bioremediation via facultative methanotrophy
FEMS Microbiology Letters, 2011Co-Authors: Jeremy D SemrauAbstract:A facultative methanotroph, Methylocystis strain SB2, was examined for its ability to degrade chlorinated hydrocarbons when grown on methane or ethanol. Strain SB2 grown on methane degraded vinyl chloride (VC), trans-dichloroethylene (t-DCE), trichloroethylene (TCE), 1,1,1-trichloroethane (1,1,1-TCA), and chloroform (CF), but not dichloromethane (DCM). Growth on methane was reduced in the presence of any chlorinated hydrocarbon. Strain SB2 grown on ethanol degraded VC, t-DCE, and TCE, and 1,1,1-TCA, but not DCM or CF. With the exception of 1,1,1-TCA, the growth of strain SB2 on ethanol was not affected by any individual chlorinated hydrocarbon. No Degradation of any chlorinated hydrocarbon was observed when acetylene was added to ethanol-grown cultures, indicating that this Degradation was due to particulate methane monooxygenase (pMMO) activity. When mixtures of chlorinated alkanes or alkenes were added to cultures growing on methane or ethanol, chlorinated alkene Degradation occurred, but chlorinated alkanes were not, and growth was reduced on both methane and ethanol. Collectively, these data indicate that competitive inhibition of pMMO activity limits methanotrophic growth and Pollutant Degradation. Facultative methanotrophy may thus be useful to extend the utility of methanotrophs for bioremediation as the use of alternative growth substrates allows for pMMO activity to be focused on Pollutant Degradation.
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mixed Pollutant Degradation by methylosinus trichosporium ob3b expressing either soluble or particulate methane monooxygenase can the tortoise beat the hare
Applied and Environmental Microbiology, 2006Co-Authors: Sung Woo Lee, David Keeney, Donghee Lim, Alan A Dispirito, Jeremy D SemrauAbstract:Methanotrophs have been widely investigated for in situ bioremediation due to their ubiquity and their ability to degrade halogenated hydrocarbons through the activity of methane monooxygenase (MMO). It has been speculated that cells expressing the soluble form of MMO (sMMO) are more efficient in cleaning up sites polluted with halogenated hydrocarbons due to its broader substrate range and relatively fast Degradation rates compared cells expressing the other form of MMO, the particulate MMO (pMMO). To examine this issue, the bioDegradation of mixtures of chlorinated solvents, i.e., trichloroethylene (TCE), trans-dichloroethylene (t-DCE), and vinyl chloride (VC), by Methylosinus trichosporium OB3b in the presence of methane using either form of MMO was investigated over longer time frames than those commonly used, i.e., days instead of hours. Growth of M. trichosporium OB3b along with Pollutant Degradation were monitored and analyzed using a simple comparative model developed from the Ω model created for analysis of the competitive binding of oxygen and carbon dioxide by ribulose bisphosphate carboxylase. From these findings, it appears that at concentrations of VC, t-DCE, and TCE greater than 10 μM each, methanotrophs expressing pMMO have a competitive advantage over cells expressing sMMO due to higher growth rates. Despite such an apparent growth advantage, pMMO-expressing cells degraded less of these substrates at these concentrations than sMMO-expressing cells during active growth. If the concentrations were increased to 100 μM, however, not only did pMMO-expressing cells grow faster, they degraded more of these Pollutants and did so in a shorter amount of time. These findings suggest that the relative rates of growth substrate and Pollutant Degradation are important factors in determining which form of MMO should be considered for Pollutant Degradation.
Anko Fischer - One of the best experts on this subject based on the ideXlab platform.
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quantification of organic Pollutant Degradation in contaminated aquifers using compound specific stable isotope analysis review of recent developments
Organic Geochemistry, 2012Co-Authors: Martin Thullner, Florian Centler, Hanshermann Richnow, Anko FischerAbstract:Abstract Compound specific stable isotope analysis (CSIA) has been established as a viable tool for proving, characterizing and assessing Degradation of organic Pollutants within contaminated aquifers. The fractionation of stable isotopes during contaminant Degradation leads to observable shifts in stable isotope ratios which can serve as an indicator for in situ Pollutant Degradation and allow for a quantitative assessment by means of the so-called Rayleigh (distillation) equation. This review highlights the recent developments of the Rayleigh equation approach for quantifying in situ Degradation of organic Pollutants in contaminated aquifers. The advantages and limitations of the Rayleigh equation approach are discussed and suggestions for improvements are given. Concepts are provided to estimate the uncertainty due to errors or variability of input parameters and how to deal with such uncertainty. Moreover, the applicability of the Rayleigh equation approach is evaluated regarding the heterogeneity and complexity of groundwater systems. For such systems, the review discusses the relevance of non-destructive processes, which affect the concentration (e.g., dispersive mixing) and potentially also the stable isotope ratio of contaminants (e.g., sorption, volatilization), and the resulting implications for the Rayleigh equation approach.
Dirk Springael - One of the best experts on this subject based on the ideXlab platform.
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carbon catabolite repression and cell dispersal affect Degradation of the xenobiotic compound 3 4 dichloroaniline in comamonas testosteroni wdl7 biofilms
FEMS Microbiology Ecology, 2017Co-Authors: Benjamin Horemans, Philip Breugelmans, Johan Hofkens, Dirk SpringaelAbstract:Organic Pollutant degrading biofilms in natural ecosystems and water treatment systems are often exposed to other carbon sources in addition to the Pollutant. The availability of auxiliary carbon sources can lead to surplus biomass growth, changes in biofilm structure and carbon catabolite repression (CCR) which together will affect Pollutant Degradation rate and efficiency of the system. To understand the interplay between these processes, continuous biofilms of the 3,4-dichloroaniline (3,4-DCA) degrading Comamonas testosteroni WDL7-RFP were grown in single- and dual-substrate conditions with 3,4-DCA and/or citrate and reciprocal effects on 3,4-DCA/citrate Degradation, biofilm biomass and biofilm structure were examined. The main mechanism affecting 3,4-DCA Degradation in biofilms in dual-substrate conditions was citrate-mediated CCR as reflected by a decrease in specific 3,4-DCA degrading activity. Growth on citrate partially compensated for the lowered specific 3,4-DCA Degradation activity under dual substrate conditions but not to the extent expected from growth observed under single-substrate conditions with citrate. This was explained by higher residual 3,4-DCA concentrations in the presence of citrate that increased cell dispersal in the biofilms. Our results show hampered Pollutant removal in biofilms due to a complex interplay of auxiliary organic C source utilization for growth affecting the specific Pollutant Degradation rate and changes in cell physiology due to increased exposure to the Pollutant as a result of lowered Pollutant Degradation rates.
Dongfeng Liu - One of the best experts on this subject based on the ideXlab platform.
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developing a base editing system to expand the carbon source utilization spectra of shewanella oneidensis mr 1 for enhanced Pollutant Degradation
Biotechnology and Bioengineering, 2020Co-Authors: Lei Cheng, Di Min, Zhouhua Cheng, Dongfeng LiuAbstract:Shewanella oneidensis MR-1, a model strain of exoelectrogenic bacteria (EEB), plays a key role in environmental bioremediation and bioelectrochemical systems because of its unique respiration capacity. However, only a narrow range of substrates can be utilized by S. oneidensis MR-1 as carbon sources, resulting in its limited applications. In this study, a rapid, highly efficient, and easily manipulated base-editing system pCBEso was developed by fusing a Cas9 nickase (Cas9n (D10A)) with the cytidine deaminase rAPOBEC1 in S. oneidensis MR-1. The C-to-T conversion of suitable C within the base-editing window could be readily and efficiently achieved by the pCBEso system without requiring double-strand break or repair templates. Moreover, double-locus simultaneous editing was successfully accomplished with an efficiency of 87.5%. With this tool, the key genes involving in N-acetylglucosamine (GlcNAc) or glucose metabolism in S. oneidensis MR-1 were identified. Furthermore, an engineered strain with expanded carbon source utilization spectra was constructed and exhibited a higher Degradation rate for multiple organic Pollutants (i.e., azo dyes and organoarsenic compounds) than the wild-type when glucose or GlcNAc was used as the sole carbon source. Such a base-editing system could be readily applied to other EEB. This study not only enhances the substrate utilization and Pollutant Degradation capacities of S. oneidensis MR-1 but also accelerates the robust construction of engineered strains for environmental bioremediation.
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enhancing extracellular electron transfer of shewanella oneidensis mr 1 through coupling improved flavin synthesis and metal reducing conduit for Pollutant Degradation
Environmental Science & Technology, 2017Co-Authors: Di Min, Feng Zhang, Lei Cheng, Xuena Huang, Dongfeng Liu, Taichu LauAbstract:Dissimilatory metal reducing bacteria (DMRB) are capable of extracellular electron transfer (EET) to insoluble metal oxides, which are used as external electron acceptors by DMRB for their anaerobic respiration. The EET process has important contribution to environmental remediation mineral cycling, and bioelectrochemical systems. However, the low EET efficiency remains to be one of the major bottlenecks for its practical applications for Pollutant Degradation. In this work, Shewanella oneidensis MR-1, a model DMRB, was used to examine the feasibility of enhancing the EET and its bioDegradation capacity through genetic engineering. A flavin biosynthesis gene cluster ribD-ribC-ribBA-ribE and metal-reducing conduit biosynthesis gene cluster mtrC-mtrA-mtrB were coexpressed in S. oneidensis MR-1. Compared to the control strain, the engineered strain was found to exhibit an improved EET capacity in microbial fuel cells and potentiostat-controlled electrochemical cells, with an increase in maximum current densi...