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 PCB-dechlorinating 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.

Thermal dechlorination of PCB-209 over Ca species-doped Fe2O3

“…The above results meant that chlorines at ortho-positions were the most stable, while those at meta-and para-positions were relatively easer to drop during catalytic degradation of PCB-209 at 300°C. The dechlorination pattern in our study was similar with that of PCB dechlorination over iron-based spinel at 300°C (Huang et al, 2013) and microbial reductive dechlorination of PCBs in soils and aquatic sediments under anaerobic conditions (Wiegel and Wu, 2000). The dechlorination pattern described above matches PCB dechlorination Process N, which defined microbiologically mediated dechlorination of PCBs which typically removes meta and/or para chlorines to generate primarily ortho-substituted lower chlorinated biphenyls (Wiegel and Wu, 2000;LaRoe et al, 2014).…”

Fate of Triclosan and Evidence for Reductive Dechlorination of Triclocarban in Estuarine Sediments

“…However, dechlorination of similar organic contaminants has been shown to be geographically variable (47). This may be related to a variety of site-specific factors including microbial species composition, competition for electron donors, and chemical inhibition (reviewed in (48)). Whether any of these factors play a role in lack of TCC dechlorination in JB sediment is unknown.…”

Use of lipid biomarkers for identification of regional sources and dechlorination characteristics of polychlorinated biphenyls in the East China Sea

“…Aerobic oxidative degradation and anaerobic reductive dechlorination have been identified to be the two main microbial processes for PCB biodegradation (Abramowicz, 1990;Wiegel and Wu, 2000). The dechlorination process typically removes the meta-and para-chlorines (Abramowicz, 1990).…”