Reductive Debromination of Polybrominated Diphenyl Ethers in Anaerobic Sediment and a Biomimetic System

Abstract

Because of the bioaccumulation of penta- and tetrapolybrominated diphenyl ether (PBDE) flame retardants in biota,the environmental biotransformation of decabromodiphenyl ether (BDE-209) is of interest. BDE-209 accounts for more than 80% by mass of PBDE production and is the dominant PBDE in sediments. Most sediments are anaerobic and reports of microbial reductive dehalogenation of hydrophobic persistent organohalogen pollutants are numerous. Reductive debromination of BDE-209 in the environment could provide a significant source of lesser-brominated PBDEs to biota. Moreover, a recent study showed that BDE-209 debrominates in sewage sludge, and another demonstrated that some halorespiring bacteria will debrominate BDE-209. To determine whether reductive debromination of BDE-209 occurs in sediments, parallel experiments were conducted using anaerobic sediment microcosms and a cosolvent-enhanced biomimetic system. In the biomimetic system, reductive debromination occurred at rates corresponding to bromine substitution levels with a BDE-209 half-life of only 18 s compared with a halflife of almost 60 days for 2,2',4,4'-tetrabromodiphenyl ether. In sediment, the measured debromination half-life of BDE-209 was well over a decade and was in good agreement with the predicted value obtained from the biomimetic experiment. Product congeners were predominantly double para-substituted. BDE-209 debrominated in sediment with a corresponding increase in nona-, octa-, hepta-, and hexa-PBDEs. Nine new PBDE congeners appeared in sediment from reductive debromination. Given the very large BDE-209 burden already in sediments globally, it is important to determine whether this transformation is a significant source of lesser-brominated PBDEs to the environment.

In vitro biotransformation of PBDEs by root crude enzyme extracts: Potential role of nitrate reductase (NaR) and glutathione S-transferase (GST) in their debromination

“…Degradation of different PBDE congeners occurred at rates corresponding to bromine substitution levels and the kinetic constant k (h À1 ) was in the following order: BDE-28 (0.00095-0.0078) < BDE-47 (0.0016-0.0079) < BDE-99 (0.0011-0.017) < BDE-209 (0.0016-0.019) ( Table S2 in the Supplementary material). BDE-209 degraded faster than BDE-99 and BDE-99 faster than BDE-47, very similar to the results obtained for PBDE debromination in a biomimetic experimental system using coenzyme vitamin B12, in which PBDEs underwent reductive debromination reactions at rates corresponding to the number of bromine substitutions (Tokarz et al, 2008). Among plant species, enzyme solution from maize roots degraded PBDEs more obviously than the ones from pumpkin and ryegrass roots, which is speculated to be ascribed to the difference in metabolic enzyme activity of different plant species (Chhikara et al, 2010).…”

Aerobic biotransformation of decabromodiphenyl ether (PBDE-209) by Pseudomonas aeruginosa

“…4(a)) which were equivalent to the total of nonabromodiphenyl ethers concentrations in technical PBDE-209 reported in the literature (Tokarz et al, 2008). In this work, two nonabromodiphenyl ethers were formed in the incubation process with the decrease of PBDE-209, demonstrating that the degradation of PBDE-209 by P. aeruginosa was accompanied by debromination.…”

Polybrominated diphenyl ethers in surface soils from e‐waste recycling areas and industrial areas in South China: Concentration levels, congener profile, and inventory

“…Microbial reductive debromination of BDE-209 and octa-BDEs mixtures under pure culture conditions has also been reported [36,37]. Furthermore, a recent study showed that BDE-209 may be degraded by microorganisms in anaerobic sediment to lessbrominated congeners, such as BDE-99, -47, and -66, and that BDE-99/-47 can also be transformed to BDE-28, BDE-17 by reductive debromination [38]. In the present study, the PCA results also indicated that some tri-and tetra-BDEs (BDE-17, -28, -66 and -71) accounted for 13.4% of the total variance (Fig.…”