Reductive Dechlorination of 1,2,3,4-Tetrachlorodibenzo-p-dioxin and Its Products by Anaerobic Mixed Cultures from Saale River Sediment

Abstract

The capability of anaerobic bacterial consortia from different environmental sources including soils, sewage sludges, and sediment of the river Saale (Germany) to dehalogenate chlorinated dioxins was compared using 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) as the model compound. The inocula were amended with mineral medium and organic acids and spiked with a high concentration (50 µM) of 1,2,3,4-TCDD to stimulate microbial dehalogenating activity. Reductive dechlorination was observed to 1,3dichlorodibenzo-p-dioxin (1,3-DCDD) as the main product and to minor amounts of the 1,2,4-and 1,2,3-trichlorodibenzop-dioxins (TrCDD) using incubations with Saale River sediment. No reaction was observed in the controls and in incubations with soils or sewage sludges. The dechlorination of 1,2,4-and 1,2,3-TrCDD was analyzed in separate subcultures. Reductive dechlorination of 1,2,4-TrCDD was a relative fast process (about 6 µM converted within 58 days) and yielded only one product (1,3-DCDD). 1,2,3-TrCDD was slowly dechlorinated to equal amounts of 1,3-and 2,3-DCDD. These observations suggest that the main dechlorination route of 1,2,3,4-TCDD to 1,3-DCDD proceeds primarily via the removal of a lateral chlorine atom with 1,2,4-TrCDD as the intermediate.

Quantifying Enhanced Microbial Dehalogenation Impacting the Fate and Transport of Organohalide Mixtures in Contaminated Sediments

“…Considering the generally slow rates of dechlorination of PCDD/Fs by dechlorinating bacteria (Adriaens et al 1995;Adriaens & Grbic-Galic 1994;Barkovskii & Adriaens 1996;Ballerstedt et al, 1997;Bunge et al, 2003;Fennell et al 2004;this (Yoshida et al, 2005;Ahn et al, 2007). Obtaining more information about the bacteria and dehalogenases involved in PCDD/F dechlorination could enable advances in using this process for bioremediation.…”

“…Biotransformation of PCDD/Fs occurs under both aerobic and anaerobic conditions (Wittich 1998;Adriaens et al, 1995;Barkowskii & Adriaens 1996Ballerstedt et al, 1997;Yoshida et al 2005). Lightly chlorinated PCDD/Fs may be biotransformed or mineralized under aerobic conditions (Wittich 1998;Yoshida et al 2005), while highly chlorinated PCDD/Fs undergo reductive dechlorination under anaerobic conditions (Adriaens et al, 1995;Barkowskii & Adriaens 1996Ballerstedt et al, 1997;Bunge et al, 2003;Fennell et al 2004).…”

“…Lightly chlorinated PCDD/Fs may be biotransformed or mineralized under aerobic conditions (Wittich 1998;Yoshida et al 2005), while highly chlorinated PCDD/Fs undergo reductive dechlorination under anaerobic conditions (Adriaens et al, 1995;Barkowskii & Adriaens 1996Ballerstedt et al, 1997;Bunge et al, 2003;Fennell et al 2004). Recently two bacterial strains have been identified which dechlorinate PCDDs under anaerobic conditions -Dehalococcoides sp.…”

“…For example, 500 ppb PCDDs were detected in the River Elbe, Germany (Götz et al, 2007); 50 ppb in the Gulf of Finland (Verta et al, 2007); 20 to 40 ppb in the Passaic River, NJ, USA (Bopp et al, 1991); and up to 90 ppb in Newark Bay, NJ, USA (Chaky, 2003). Freshly added (Adriaens et al, 1995;Ballerstedt et al, 1997;Vargas et al, 2001;Ahn et al, 2005) and existing PCDDs (Albrecht et al, 1999;Yoshida et al, 2005) were dechlorinated under anaerobic conditions. However, with few exceptions (Lohmann et al, 2000;Bunge et al, 2007), lightly chlorinated PCDDs are not routinely measured in environmental samples, thus there is little historical data documenting environmental PCDD dechlorination.…”

“…Dechlorination of freshly spiked PCDD congeners in anaerobic microcosms and enrichment cultures has been observed (Adriaens & Grbic-Galic, 1994;Barkovskii & Adriaens, 1996;Ballerstedt et al, 1997;Kao et al, 2001;Bunge et al, 2001). This dechlorination can be stimulated by amending halogenated structural analogues as co-substrates, also known as "haloprimers" (Vargas et al, 2001, Fu et al, 2005Ahn et al, 2005Ahn et al, , 2007, as previously shown for PCBs (Bedard et al, 1998).…”