Riboflavin- and cobalamin-mediated biodegradation of chloroform in a methanogenic consortium

Claudia Guerrero-Barajas, James A Field

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Chloroform (CF) is an important priority pollutant contaminating groundwater. Reductive dechlorination by anaerobic microorganisms is a promising strategy towards the remediation of CF. The objective of this study was to evaluate the use of redox active vitamins as electron shuttles to enhance the anaerobic biodegradation of CF in an unadapted methanogenic consortium not previously exposed to chlorinated compounds. Only negligible degradation of CF was observed in control cultures lacking redox active vitamins. The addition of riboflavin (RF), cyanocobalamin (CNB12), and hydroxycobalamin (HOB12) enabled biodegradation of CF. The reactions were predominantly catalyzed biologically as evidenced by the lack of any CF conversion in heat-killed controls amended with the cobalamins or minor conversion with RF. In live cultures, significant increases in the rate of CF conversion was observed at substoichiometric molar ratios as low as 0.1 to 0.01 vitamin:CF for RF and CNB12, respectively. At the highest molar vitamin:CF ratios tested of 0.2, the first-order rate constant of CF degradation was 5.3- and 91-fold higher in RF and CNB12 amended cultures, respectively, compared to the unamended control culture. The distribution of biotransformation products was highly impacted by the type of redox active vitamin utilized. Cultures supplemented with RF provided high yields of dichloromethane (DCM). On the other hand, cobalamins promoted the near complete mineralization of organochlorine in CF to inorganic chloride and lowered the yield of DCM. In cultures where no or little CF bioconversion occurred, prolonged exposure to CF resulted in cell lysis, as evidenced by the release of intracellular chloride. The results taken as a whole suggest that the anaerobic bioremediation of CF-contaminated sites can greatly be improved with strategies aimed at increasing the concentration of redox active vitamins.

Original languageEnglish (US)
Pages (from-to)539-550
Number of pages12
JournalBiotechnology and Bioengineering
Volume89
Issue number5
DOIs
StatePublished - Mar 5 2005

Fingerprint

Riboflavin
Vitamin B 12
Chloroform
Chlorine compounds
Biodegradation
Vitamins
Oxidation-Reduction
Methylene Chloride
Dichloromethane
Chlorides
Hydroxocobalamin
Degradation
Bioconversion
Dechlorination
Environmental Biodegradation
Bioremediation
Groundwater
Biotransformation
Remediation
Microorganisms

Keywords

  • Anaerobic
  • Bioremediation
  • Chloromethanes
  • Dehalogenation
  • Redox mediators
  • Reductive dechlorination
  • Trichloromethane
  • Vitamin B12

ASJC Scopus subject areas

  • Biotechnology
  • Microbiology

Cite this

Riboflavin- and cobalamin-mediated biodegradation of chloroform in a methanogenic consortium. / Guerrero-Barajas, Claudia; Field, James A.

In: Biotechnology and Bioengineering, Vol. 89, No. 5, 05.03.2005, p. 539-550.

Research output: Contribution to journalArticle

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abstract = "Chloroform (CF) is an important priority pollutant contaminating groundwater. Reductive dechlorination by anaerobic microorganisms is a promising strategy towards the remediation of CF. The objective of this study was to evaluate the use of redox active vitamins as electron shuttles to enhance the anaerobic biodegradation of CF in an unadapted methanogenic consortium not previously exposed to chlorinated compounds. Only negligible degradation of CF was observed in control cultures lacking redox active vitamins. The addition of riboflavin (RF), cyanocobalamin (CNB12), and hydroxycobalamin (HOB12) enabled biodegradation of CF. The reactions were predominantly catalyzed biologically as evidenced by the lack of any CF conversion in heat-killed controls amended with the cobalamins or minor conversion with RF. In live cultures, significant increases in the rate of CF conversion was observed at substoichiometric molar ratios as low as 0.1 to 0.01 vitamin:CF for RF and CNB12, respectively. At the highest molar vitamin:CF ratios tested of 0.2, the first-order rate constant of CF degradation was 5.3- and 91-fold higher in RF and CNB12 amended cultures, respectively, compared to the unamended control culture. The distribution of biotransformation products was highly impacted by the type of redox active vitamin utilized. Cultures supplemented with RF provided high yields of dichloromethane (DCM). On the other hand, cobalamins promoted the near complete mineralization of organochlorine in CF to inorganic chloride and lowered the yield of DCM. In cultures where no or little CF bioconversion occurred, prolonged exposure to CF resulted in cell lysis, as evidenced by the release of intracellular chloride. The results taken as a whole suggest that the anaerobic bioremediation of CF-contaminated sites can greatly be improved with strategies aimed at increasing the concentration of redox active vitamins.",
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