Microbial degradation of 4-monobrominated diphenyl ether in an aerobic sludge and the DGGE analysis of diversity

Abstract

Polybrominated diphenyl ethers (PBDEs) were applied as flame retardant additives in polymers for many plastic and electronic products. Due to their ubiquitous distribution in the environment, potential toxicity to human and tendency for bioaccumulation, PBDEs have raised public safety concern. In this study we examined the degradation of 4-monobrominated diphenyl ether (4-BDE) in aerobic sludge, as a model for PBDE biodegradation. Degradation of 4-BDE was observed in aerobic sludge. Co-metabolism with toluene or diphenyl ether facilitated 4-BDE biodegradation in terms of kinetics and efficiency. Diphenyl ether seems to perform slightly better as an auxiliary carbon source than toluene in facilitating 4-BDE degradation. During the experiment we identified diphenyl ether by gas chromatography/mass spectrometry(GC/MS), which indicates that an anaerobic debromination has occurred. Bacterial community composition was monitored with denaturing gradient gel electrophoresis. The fragments enriched in 4-BDE-degrading aerobic sludge samples belong to presumably a novel anaerobic Clostridiales species distantly related to all known debrominating microbes. This suggests that 4-BDE biodegradation can occur in anaerobic micro-niche in an apparently aerobic environment, by a previously unknown bacterial species. These findings can provide better understandings of biodegradation of brominated diphenyl ethers and can facilitate the prediction of the fate of PBDEs in the environment.

Anaerobic degradation of Polychlorinated Biphenyls (PCBs) and Polychlorinated Biphenyls Ethers (PBDEs), and microbial community dynamics of electronic waste-contaminated soil

“…Previous studies showed that aerobic bacteria play an important role in the biodegradation of halogenated compounds with less than five halogen atoms (Chang et al, 2013;Chen et al, 2010). Aerobic bacterium with the ability of debrominating deca-BDE was also isolated from sediment by Deng (Deng et al, 2011); while for the microbial degradation of higher halogenated compounds, it was proved by different researches that the compounds were dehalogenated under anaerobic conditions by various anaerobic bacteria (Bedard, 2003;Bedard et al, 2005;He et al, 2006;Tokarz et al, 2008;Yen et al, 2009).…”

“…Aerobic and anaerobic biodegradation of such compounds have been investigated extensively (Bedard, 2003;Chang et al, 2013;Chen et al, 2010;Cutter et al, 2001;Dabrowska and Rosinska, 2012;Deng et al, 2011;Fennell et al, 2004;Li et al, 2005;Payne et al, 2011Payne et al, , 2013Rayne et al, 2003;Shih et al, 2012). Aerobic microbial degradation is often possible only when halogenated compounds have a maximum of four-to-five halogen atoms, although an aerobic bacterium responsible for deca-BDE debromination was isolated from sediment (Deng et al, 2011).…”

Polybrominated diphenyl ethers disrupt molting in neonatal Daphnia magna

“…The three commercial formulations vary in their critical effects and effective doses-with the penta-BDEs appearing to cause adverse effects at comparably lower doses, and deca-BDE at higher doses (Darnerud 2003). Higher brominated PBDEs can be debrominated to lower brominated congeners in biota (Stapleton et al 2004;Roberts et al 2011;Stapleton et al 2006) or in the environment, by exposure to UV light (Soderstrom et al 2004) or by microbial degradation (Chen et al 2010). Numerous studies have identified a range of adverse effects in wildlife and humans after exposure to PBDEs (Darnerud 2003(Darnerud , 2008.…”

Microbial Degradation of Some Halogenated Compounds: Biochemical and Molecular Features

“…In our previous study, the mono-BDE is transformed to diphenyl ether in an aerobic culture from sewage sediment, indicating an anaerobic debromination reaction occurred. The enriched Clostridiales specie shown in the denatured gradient gel electrophoresis (DGGE) may responsible for such reaction [55].…”