Anaerobic dechlorination of trichloroethene, tetrachloroethene and 1,2-dichloroethane by an acetogenic mixed culture in a fixed-bed reactor

Abstract

An anaerobic enrichment culture with glucose as the sole source of carbon and energy plus trichloroethene (TCE) as a potential electron acceptor was inoculated with material from a full size anaerobic charcoal reactor that biologically eliminated dichloromethane from contaminated groundwater (Stromeyer et al. 1991). In subcultures of this enrichment complete sequential transformation of 10 microM TCE via cis-dichloroethene and chloroethene to ethene was reproducibly observed. Maintenance of this activity on subcultivation required the presence of TCE in the medium. The enrichment culture was used to inoculate an anaerobic fixed-bed reactor containing sintered glass Raschig elements as support material. The reactor had a total volume of 1780 ml and was operated at 20 degrees C in an up-flow mode with a flow rate of 50 ml/h. It was fed continuously with 2 mM glucose and 55 microM TCE. Glucose was converted to acetate as the major product and to a minor amount of methane; TCE was quantitatively dehalogenated to ethene. When, in addition to TCE, tetrachloroethene or 1,2-dichloroethane were added to the system, these compounds were also dehalogenated to ethene. In contrast, 1,1,1-trichloroethane was not dehalogenated, but at 40 microM severely inhibited acetogenesis and methanogenesis. When the concentration of TCE in the feed was raised to 220 microM, chloroethene transiently accumulated, but after an adaptation period ethene was again the only volatile product detected in the effluent. The volumetric degradation rate at this stage amounted to 6.2 mumol/l/h.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation of Acetobacterium sp. Strain AG, Which Reductively Debrominates Octa- and Pentabrominated Diphenyl Ether Technical Mixtures

“…belong to acetogens, whose presence is ubiquitous in the environment (44). Although reductive dehalogenation by acetogens has been implicated for chloroethanes and chloroethenes (45)(46)(47), they are rarely shown to dehalogenate brominated/aromatic compounds, with only one such reported case (i.e., Desulfitobacterium chlororespirans strain Co23 on an octa-BDE mixture but with no detailed debromination profile or kinetics [12,48]). The acetogenic autotroph Acetobacterium sp.…”

Molecular Characterization of a Dechlorinating Community Resulting from In Situ Biostimulation in a Trichloroethene-Contaminated Deep, Fractured Basalt Aquifer and Comparison to a Derivative Laboratory Culture

“…Microorganisms with enzymes from the acetyl-coenzyme A pathway, including acetogens and acetoclastic methanogens, may play a role in this first stage of dechlorination due to an abundance of transition metal corrinoid cofactors (15,20,42). Corrinoid-dependent dechlorination has been demonstrated in methanogenic and acetogenic consortia and isolates (6,19,24,26,40,41,(79)(80)(81)(82)84), as well as dehalorespiratory isolates (1,27,41,44,52,59,67,70). Our knowledge of microorganisms that can participate in the second stage of dechlorination, namely, the reduction of cis-DCE and VC, is currently limited to the genus Dehalococcoides (11,33,56).…”

Isolation of an anaerobic bacterium which reductively dechlorinates tetrachloroethene and trichloroethene

“…The growth medium used in the present work (medium A) was similar to the medium described previously (Wild et al 1995), except that 55 mM carbonate was used as buffer, 1.0 mM of titanium citrate (Zehnder & Wuhrmann 1976) as reductant and H2/CO2 (80%/20%, v/v) at 2.8 bar as the gas phase. 5% (v/v) of filtersterilized spent medium from the fixed-bed reactor was added as a source of growth factors.…”

“…5% (v/v) of filtersterilized spent medium from the fixed-bed reactor was added as a source of growth factors. The fixed-bed reactor (1.2 liter) providing the spent medium has been described (Wild et al 1995)• It was continuously fed at 20 °C with 2 mM glucose and 55 ~tM tichloroethene at a flow rate of 50 ml/h. All cultures were incubated on a rotary shaker at 30 °C in the dark.…”