23 Citations (Scopus)

Abstract

Background: Buffering to achieve pH control is crucial for successful trichloroethene (TCE) anaerobic bioremediation. Bicarbonate (HCO3 -) is the natural buffer in groundwater and the buffer of choice in the laboratory and at contaminated sites undergoing biological treatment with organohalide respiring microorganisms. However, HCO3 - also serves as the electron acceptor for hydrogenotrophic methanogens and hydrogenotrophic homoacetogens, two microbial groups competing with organohalide respirers for hydrogen (H2). We studied the effect of HCO3 - as a buffering agent and the effect of HCO3 --consuming reactions in a range of concentrations (2.5-30 mM) with an initial pH of 7.5 in H2-fed TCE reductively dechlorinating communities containing Dehalococcoides, hydrogenotrophic methanogens, and hydrogenotrophic homoacetogens.Results: Rate differences in TCE dechlorination were observed as a result of added varying HCO3 - concentrations due to H2-fed electrons channeled towards methanogenesis and homoacetogenesis and pH increases (up to 8.7) from biological HCO3 - consumption. Significantly faster dechlorination rates were noted at all HCO3 - concentrations tested when the pH buffering was improved by providing 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) as an additional buffer. Electron balances and quantitative PCR revealed that methanogenesis was the main electron sink when the initial HCO3 - concentrations were 2.5 and 5 mM, while homoacetogenesis was the dominant process and sink when 10 and 30 mM HCO3 - were provided initially.Conclusions: Our study reveals that HCO3 - is an important variable for bioremediation of chloroethenes as it has a prominent role as an electron acceptor for methanogenesis and homoacetogenesis. It also illustrates the changes in rates and extent of reductive dechlorination resulting from the combined effect of electron donor competition stimulated by HCO3 - and the changes in pH exerted by methanogens and homoacetogens.

Original languageEnglish (US)
Article number128
JournalMicrobial Cell Factories
Volume11
DOIs
StatePublished - Sep 13 2012

Fingerprint

Dechlorination
Bicarbonates
Buffers
Electrons
Methanogens
Trichloroethylene
Environmental Biodegradation
Bioremediation
HEPES
Groundwater
Microorganisms
Hydrogen
Polymerase Chain Reaction
Acids

Keywords

  • Acetogen
  • Alkalinity
  • Bicarbonate competition
  • Dehalococcoides
  • pH range
  • Trichloroethylene

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology

Cite this

Role of bicarbonate as a pH buffer and electron sink in microbial dechlorination of chloroethenes. / Delgado, Anca; Parameswaran, Prathap; Fajardo-Williams, Devyn; Halden, Rolf; Krajmalnik-Brown, Rosa.

In: Microbial Cell Factories, Vol. 11, 128, 13.09.2012.

Research output: Contribution to journalArticle

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abstract = "Background: Buffering to achieve pH control is crucial for successful trichloroethene (TCE) anaerobic bioremediation. Bicarbonate (HCO3 -) is the natural buffer in groundwater and the buffer of choice in the laboratory and at contaminated sites undergoing biological treatment with organohalide respiring microorganisms. However, HCO3 - also serves as the electron acceptor for hydrogenotrophic methanogens and hydrogenotrophic homoacetogens, two microbial groups competing with organohalide respirers for hydrogen (H2). We studied the effect of HCO3 - as a buffering agent and the effect of HCO3 --consuming reactions in a range of concentrations (2.5-30 mM) with an initial pH of 7.5 in H2-fed TCE reductively dechlorinating communities containing Dehalococcoides, hydrogenotrophic methanogens, and hydrogenotrophic homoacetogens.Results: Rate differences in TCE dechlorination were observed as a result of added varying HCO3 - concentrations due to H2-fed electrons channeled towards methanogenesis and homoacetogenesis and pH increases (up to 8.7) from biological HCO3 - consumption. Significantly faster dechlorination rates were noted at all HCO3 - concentrations tested when the pH buffering was improved by providing 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) as an additional buffer. Electron balances and quantitative PCR revealed that methanogenesis was the main electron sink when the initial HCO3 - concentrations were 2.5 and 5 mM, while homoacetogenesis was the dominant process and sink when 10 and 30 mM HCO3 - were provided initially.Conclusions: Our study reveals that HCO3 - is an important variable for bioremediation of chloroethenes as it has a prominent role as an electron acceptor for methanogenesis and homoacetogenesis. It also illustrates the changes in rates and extent of reductive dechlorination resulting from the combined effect of electron donor competition stimulated by HCO3 - and the changes in pH exerted by methanogens and homoacetogens.",
keywords = "Acetogen, Alkalinity, Bicarbonate competition, Dehalococcoides, pH range, Trichloroethylene",
author = "Anca Delgado and Prathap Parameswaran and Devyn Fajardo-Williams and Rolf Halden and Rosa Krajmalnik-Brown",
year = "2012",
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doi = "10.1186/1475-2859-11-128",
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T1 - Role of bicarbonate as a pH buffer and electron sink in microbial dechlorination of chloroethenes

AU - Delgado, Anca

AU - Parameswaran, Prathap

AU - Fajardo-Williams, Devyn

AU - Halden, Rolf

AU - Krajmalnik-Brown, Rosa

PY - 2012/9/13

Y1 - 2012/9/13

N2 - Background: Buffering to achieve pH control is crucial for successful trichloroethene (TCE) anaerobic bioremediation. Bicarbonate (HCO3 -) is the natural buffer in groundwater and the buffer of choice in the laboratory and at contaminated sites undergoing biological treatment with organohalide respiring microorganisms. However, HCO3 - also serves as the electron acceptor for hydrogenotrophic methanogens and hydrogenotrophic homoacetogens, two microbial groups competing with organohalide respirers for hydrogen (H2). We studied the effect of HCO3 - as a buffering agent and the effect of HCO3 --consuming reactions in a range of concentrations (2.5-30 mM) with an initial pH of 7.5 in H2-fed TCE reductively dechlorinating communities containing Dehalococcoides, hydrogenotrophic methanogens, and hydrogenotrophic homoacetogens.Results: Rate differences in TCE dechlorination were observed as a result of added varying HCO3 - concentrations due to H2-fed electrons channeled towards methanogenesis and homoacetogenesis and pH increases (up to 8.7) from biological HCO3 - consumption. Significantly faster dechlorination rates were noted at all HCO3 - concentrations tested when the pH buffering was improved by providing 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) as an additional buffer. Electron balances and quantitative PCR revealed that methanogenesis was the main electron sink when the initial HCO3 - concentrations were 2.5 and 5 mM, while homoacetogenesis was the dominant process and sink when 10 and 30 mM HCO3 - were provided initially.Conclusions: Our study reveals that HCO3 - is an important variable for bioremediation of chloroethenes as it has a prominent role as an electron acceptor for methanogenesis and homoacetogenesis. It also illustrates the changes in rates and extent of reductive dechlorination resulting from the combined effect of electron donor competition stimulated by HCO3 - and the changes in pH exerted by methanogens and homoacetogens.

AB - Background: Buffering to achieve pH control is crucial for successful trichloroethene (TCE) anaerobic bioremediation. Bicarbonate (HCO3 -) is the natural buffer in groundwater and the buffer of choice in the laboratory and at contaminated sites undergoing biological treatment with organohalide respiring microorganisms. However, HCO3 - also serves as the electron acceptor for hydrogenotrophic methanogens and hydrogenotrophic homoacetogens, two microbial groups competing with organohalide respirers for hydrogen (H2). We studied the effect of HCO3 - as a buffering agent and the effect of HCO3 --consuming reactions in a range of concentrations (2.5-30 mM) with an initial pH of 7.5 in H2-fed TCE reductively dechlorinating communities containing Dehalococcoides, hydrogenotrophic methanogens, and hydrogenotrophic homoacetogens.Results: Rate differences in TCE dechlorination were observed as a result of added varying HCO3 - concentrations due to H2-fed electrons channeled towards methanogenesis and homoacetogenesis and pH increases (up to 8.7) from biological HCO3 - consumption. Significantly faster dechlorination rates were noted at all HCO3 - concentrations tested when the pH buffering was improved by providing 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) as an additional buffer. Electron balances and quantitative PCR revealed that methanogenesis was the main electron sink when the initial HCO3 - concentrations were 2.5 and 5 mM, while homoacetogenesis was the dominant process and sink when 10 and 30 mM HCO3 - were provided initially.Conclusions: Our study reveals that HCO3 - is an important variable for bioremediation of chloroethenes as it has a prominent role as an electron acceptor for methanogenesis and homoacetogenesis. It also illustrates the changes in rates and extent of reductive dechlorination resulting from the combined effect of electron donor competition stimulated by HCO3 - and the changes in pH exerted by methanogens and homoacetogens.

KW - Acetogen

KW - Alkalinity

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KW - Dehalococcoides

KW - pH range

KW - Trichloroethylene

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