Monochloro- and dichloroacetic acids as carbon and energy sources for a stable, methanogenic mixed culture

Abstract

Abstract.A stable methanogenic mixed culture was enriched from an industrial environment to utilize chloroacetate as sole carbon and energy source for growth. It immobilized spontaneously on activated charcoal and grew reproducibly on this carrier in a fluidized bed reactor when supplied with an anaerobic mineral salts medium. Substrate disappearance was complete. Methane, CO2 and chloride ions were conclusively identified as the metabolic products and quantified. The growth yield from chloroacetate was about I g of protein/mol of carbon. The calculated degradation rate in the fluidized bed reactor was 0.2 to 0.8 mmol/1-h. The first metabolic intermediate from [2-13C]monochloroacetat e in portions of biofilm-coated carrier was shown by 13C_NM R to be glycolate, from which 13C02 and 13CH4 were formed. Glycolate was formed in an oxygen-insensitive hydrolysis, but its conversion to C02 and CH4 was strictly anaerobic and sensitive to inhibition by bromoethanesulfonate. Degradation of [1-14C]-and [2-14C]_chloroacetat e each yielded the same amount of [14C]-methane. We thus presume glycolate to be cleaved to CO2 and Ha, which were the substrates for methanogenesis. Dehalogenation was limited to chloro-, bromo-, iodo-and dichloroacetate. These four compounds and glycolate were utilized as the sole carbon and energy sources by the methanogenic mixed culture.

Dichloromethane utilized by an anaerobic mixed culture: acetogenesis and methanogenesis

“…Indeed, the only haloaliphatic compound currently known to serve as a carbon and energy source for anaerobic growth is chloroacetate (Egli et al 1989). We now report that DCM can be utilized as the sole source of carbon and energy by an anaerobic mixed culture, and that the anaerobic treatment of waste DCM is possible.…”

“…Formate was analyzed enzymatically (Schaller & Triebig 1984). Chloride ion in biological samples was determined spectrophotometrically (Bergmann & Sanik 1957) after oxidation of thiols (Egli et al 1989). The identification of the chloride ion was confirmed by ion-chromatography with suppressor (AS4A column; Dionex, Sunnyvale, USA).…”

Anaerobic degradation of tetrachloromethane by Acetobacterium woodii: separation of dechlorinative activities in cell extracts and roles for vitamin B12 and other factors

“…The anaerobic glovebox (Egli et al 1989), HPLC, GC-TCD, liquid scintillation counter and spectrophotometer (Egli et al 1988), GC-FID equipped with a methanizer (8700; Perkin Elmer, Beaconsfield, Bucks, UK), GC-MS (5890-5870, Hewlett-Packard, Avondale, PA) and atom absorption spectrophotometer equipped with a graphite tube atomizer (Spectra AA400/GTA-96; Varian, Palo Alto, CA) were commercially-available equipment. FPLC was done with LKB apparatus (Pharmacia/LKB) attached to a fraction collector (2110; Bio-Rad, Richmond, CA, USA) which could be passed into the glovebox, and which was adapted to allow collection of samples under anaerobic conditions.…”

Reductive Dehalogenation of Trichloroacetic Acid by Trichlorobacter thiogenes gen. nov., sp. nov

“…In contrast, TCA degradation in anaerobic conditions has not yet been described. Only one report was found which mentions TCA disappearance in a reactor with an immobilized methanogenic mixed culture, but the authors ascribe TCA transformation to a combination of chemical and biological reactions (4). The isolation of a bacterium able to grow via reductive TCA dechlorination clearly establishes the existence of an anaerobic TCA removal process.…”

“…In addition, the reducing agents were 0.2 mM concentrations of both L-cysteine and Na 2 S.9H 2 O instead of 1 mM Na 2 S.9H 2 O alone, since high sulfide concentrations interfere with chloride determinations (4). After the addition of a 1% inoculum to the medium, samples were taken at regular intervals to monitor the TCA, DCA, MCA, and chloride concentrations.…”