Microbial reductive dehalogenation of polychlorinated biphenyls

Abstract

Under anaerobic conditions, microbial reductive dechlorination of polychlorinated biphenyls (PCBs) occurs in soils and aquatic sediments. In contrast to dechlorination of supplemented single congeners for which frequently ortho dechlorination has been observed, reductive dechlorination mainly attacks meta and/or para chlorines of PCB mixtures in contaminated sediments, although in a few instances ortho dechlorination of PCBs has been observed. Different microorganisms appear to be responsible for different dechlorination activities and the occurrence of various dehalogenation routes. No axenic cultures of an anaerobic microorganism have been obtained so far. Most probable number determinations indicate that the addition of PCB congeners, as potential electron acceptors, stimulates the growth of PCBdechlorinating microorganisms. A few PCB-dechlorinating enrichment cultures have been obtained and partially characterized. Temperature, pH, availability of naturally occurring or of supplemented carbon sources, and the presence or absence of H 2 or other electron donors and competing electron acceptors influence the dechlorination rate, extent and route of PCB dechlorination. We conclude from the sum of the experimental data that these factors influence apparently the composition of the active microbial community and thus the routes, the rates and the extent of the dehalogenation. The observed effects are due to the specificity of the dehalogenating bacteria which become active as well as changing interactions between the dehalogenating and non-dehalogenating bacteria. Important interactions include the induced changes in the formation and utilization of H 2 by non-dechlorinating and dechlorinating bacteria, competition for substrates and other electron donors and acceptors, and changes in the formation of acidic fermentation products by heterotrophic and autotrophic acidogenic bacteria leading to changes in the pH of the sediments. ß

Reductive Dechlorination of Polychlorinated Biphenyls in Sediment From the Twelve Mile Creek Arm of Lake Hartwell, South Carolina, Usa

“…No other organic acids were detected. Sediment typically supplies the electron donor needed by PCB dechlorinators as well as substrates for non- dechlorinators that likely provide the dechlorinators with growth factors [22]. 3D), while initially none occurred in G30 (Fig.…”

Polychlorinated biphenyl (PCB) anaerobic degradation in marine sediments: microcosm study and role of autochthonous microbial communities

“…Even if the industrial production of PCBs has been banned since the late 1970s, the chronic toxicity of these recalcitrant hazardous substances still remains, and the decontamination of lakes, rivers, harbors, and marine sediment continues to represent a challenge today (ATSDR 2000;Furukawa and Fujihara 2008;Robertson and Hansen 2015). microbial dechlorination processes have been identified with the chlorine to be removed in various positions (processes M, Q, H', H, P, N, LP, and T) (Wiegel and Wu 2000;Bedard 2003). Anaerobic reductive dechlorination (RD) is the only process known to convert PCBs (chlorinated in para and meta positions) into less chlorinated congeners with a lower toxicity (e.g., ortho-chlorines) (Brown et al 1987;Wu et al 2002;Borja et al 2005;Bedard 2008;Passatore et al 2014;Kimbrough and Goyer 1985;Safe 1989;Quensen et al 1990Quensen et al , 1998Field and Sierra-Alvarez 2008).…”

“…In addition, the occurrence and the rate of dehalogenation are strongly dependent on the nature of the microbial population, the metabolic specificity of which depends on the number and position of chlorines on the phenyl rings and on the availability of electron donors (Wiegel and Wu 2000).…”

“…Over the last few years, several Dhc strains with various dechlorinating capabilities have been isolated (i.e., Dhc strains 195, VS, GT, H10, BAV1, CBDB1, JNA) (Sung et al 2006;Copeland et al 2007a, b;He et al 2005;Kube et al 2005;Adrian et al 2009;Loeffler et al 2013;Laroe et al 2014;Kube et al 2005;Bedard et al 2007;Pieper and Seeger 2008;Laroe et al 2014;Fricker et al 2014). Moreover, PCB biodegradation has been also attributed to Dhc strains CDBD1 and 195, the activity of which has been reported in environmental matrices or microcosm studies (Brown et al 1987;Bedard et al 2005;Wiegel and Wu 2000). JNA is the only Dhc strain reported to be able to mediate the anaerobic degradation of hexa-CBs and hepta-CBs by process N into byproducts, which can be aerobically degraded into di-and tri-CBs by processes LP or Q (Bedard 2003;Bedard and Quensen 1995;Pieper 2005;Field and Sierra-Alvarez 2008;Laroe et al 2014).…”

Microbial reductive dechlorination of pre-existing PCBs and spiked 2,3,4,5,6-pentachlorobiphenyl in anaerobic slurries of a contaminated sediment of Venice Lagoon (Italy)

“…They are poorly biodegradable, highly hydrophobic, and accumulate in sub‐surface sediments which are the ultimate sinks for PCBs released into aquatic systems [2]. The occurrence of microbial‐mediated, reductive dechlorination processes towards PCBs has been documented in a variety of anaerobic freshwater sediments [3,4]. The process, generally consisting of the conversion of highly chlorinated, meta ‐ and para ‐substituted PCBs into low‐chlorinated, ortho ‐substituted biphenyls, has often been ascribed to the activity of indigenous methanogenic microorganisms capable of fortuitously using PCBs as terminal electron acceptors [3,4].…”