Tetrabrominated Diphenyl Ether Research Articles

Degradation of Benzo[a]pyrene and 2,2',4,4'-Tebrabrominated Diphenyl Ether in Cultures Originated from an Agricultural Soil.

Benzo[a]pyrene (BaP) and 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) are common contaminants in the environment, posing a threat to the ecosystems and human health. Currently, information on the microbial metabolism of BaP and BDE-47 as well as the correlated bacteria is still limited. This research aimed to study the degradation of BaP and BDE-47 by enriched cultures originated from an agricultural soil in Tianjin (North China) and characterize the bacteria involved in the degradation. Two sets of experiments were set up with BaP and BDE-47 (2 mg/L) as the sole carbon source, respectively. The degradation of BaP and BDE-47 occurred at rate constants of 0.030 /d and 0.026 /d, respectively. For BaP, the degradation products included benzo[a]pyrene-9,10-dihydrodiol or its isomers, ben-zo(a)pyrene-7,8-dihydrodiol-9,10-epoxide, and cis-4 (8-hydroxypyrenyl-7)-2-oxo-3-butenoic acid. For BDE-47, the degradation products included 2,2',4-tribrominated diphenyl ether (BDE-17), 2,4-dibrominated diphenyl ether (BDE-7), and hydroxylated dibromodiphenyl ether. The bacterial community structures in the original soil, the BaP culture, and the BDE-47 culture were quite different. The richness and diversity of bacteria in the two cultures were much lower than that in the original soil, and the BaP culture had higher richness and diversity than the BDE-47 culture. In the BaP culture, multiple species such as Niabella (23.4%), Burkholderia-Caballeronia-Paraburkholderia (13.7%), Cupriavidus (8.3%), and Allorhizobi-um-Neorhizobium-Pararhizobium-Rhizobium (8.0%) were dominant. In the BDE-47 culture, an unassigned species in the Rhizobiaceae was dominant (82.3%). The results from this study provide a scientific basis for the risk assessment and bioremediation of BaP and/or BDE-47 in a contaminated environment.

Novel Insights into Uptake, Translocation, and Transformation Mechanisms of 2,2',4,4'-Tetra Brominated Diphenyl Ether (BDE-47) in Wheat (Triticum aestivum L.): Implication by Compound-Specific Stable Isotope and Transcriptome Analysis.

The uptake, translocation, and transformation of 2,2',4,4'-tetra brominated diphenyl ether (BDE-47) in wheat (Triticum aestivum L.) were comprehensively investigated by hydroponic experiments using compound-specific stable isotope analysis (CSIA) and transcriptome analysis. The results indicated that BDE-47 was quickly adsorbed on epidermis of wheat roots and then absorbed in roots via water and anion channels as well as an active process dependent on energy. A small fraction of BDE-47 in roots was subjected to translocation acropetally, and an increase of δ13C values in shoots than roots implied that BDE-47 in roots had to cross at least one lipid bilayer to enter the vascular bundle via transporters. In addition, accompanied by the decreasing concentrations, δ13C values of BDE-47 showed the increasing trend with time in shoots, indicating occurrence of BDE-47 transformation. OH-PBDEs were detected as transformation products, and the hydroxyl group preferentially substituted at the ortho-positions of BDE-47. Based on transcriptome analysis, genes encoding polybrominated diphenyl ether (PBDE)-metabolizing enzymes, including cytochrome P450 enzymes, nitrate reductases, and glutathione S-transferases, were significantly upregulated after exposure to BDE-47 in shoots, further evidencing BDE-47 transformation. This study first reported the stable carbon isotope fractionation of PBDEs during translocation and transformation in plants, and application of CSIA and transcriptome analysis allowed systematically characterize the environmental behaviors of pollutants in plants.

Bioremediation of PBDEs and heavy metals co-contaminated soil in e-waste dismantling sites by Pseudomonas plecoglossicida assisted with biochar

Biochar-assisted microbial remediation has been proposed as a promising strategy to eliminate environmental pollutants. However, studies on this strategy used in the remediation of persistent organic pollutants and heavy metals co-contaminated soil are lacking, and the effect of the combined incorporation of biochar and inoculant on the assembly, functions, and microbial interactions of soil microbiomes are unclear. Here, we studied 2,2′,4,4′-tetrabrominated diphenyl ether (BDE-47) degradation and heavy metal immobilization by and biochar-based bacterial inoculant (BC/PP) in an e-waste contaminated soil, and corresponding microbial regulation mechanisms. Results showed that BC/PP addition was more effective in reducing Cu and Pb availability and degrading BDE-47 than inoculant alone. Notably, BC/PP facilitated bound-residue formation of BDE-47, reducing the ecological risk of residual BDE-47. Meanwhile, microbial carbon metabolism and enzyme activities (related to C-, N-, and P- cycles) were enhanced in soil amended with BC/PP. Importantly, biochar played a crucial role in inoculant colonization, community assembly processes, and microbiome multifunction. In the presence of biochar, positive interactions in co-occurrence networks of the bacterial community were more frequent, and higher network stability and more keystone taxa were observed (including potential degraders). These findings provide a promising strategy for decontaminating complex-polluted environments and recovering soil ecological functions.

2,2′,4,4′-tetrabromodiphenyl ether causes depigmentation in zebrafish larvae via a light-mediated pathway

Polybrominated diphenyl ethers (PBDEs) are organic pollutants widely detected in various environmental media due to their high persistence and bioaccumulation. PBDE-induced visual impairment and neurotoxicity were previously demonstrated using zebrafish (Danio rerio) models, and recent research reported the phenotypic depigmentation effect of PBDEs at high concentrations on zebrafish, but whether those effects are still present at environment-relevant levels is still unclear. Herein, we performed both phenotypic examination and mechanism investigation in zebrafish embryos (48 hpf) and larvae (5 dpf) about their pigmentation status when exposing to PBDE congener BDE-47 (2,2′,4,4′-tetrabrominated diphenyl ether) at levels from 0.25 to 25 μg/L. Results showed that low-level BDE-47 can restrain the relative melanin abundance of zebrafish larvae to 70.47% (p < 0.05) and 61.54% (p < 0.01) respectively under 2.5 and 25 μg/L BDE-47 compared with control, and the thickness of retinal pigment epithelium (RPE) remarkably reduced from 571.4 nm to 350.3 nm (p < 0.001) under 25 μg/L BDE-47 exposure. We also observed disrupted expressions of melanin synthesis genes and disorganized mitfa differentiation patterns based on Tg(mifta:EGFP), as well as visual impairment resulting from thinner RPE. Considering both processes of visual development and melanin synthesis are highly sensitive to ambient light conditions, we prolonged the light regime of maintaining zebrafish larvae from 14 hours light versus 10 hours dark (14L:10D) to 18 hours light versus 6 hours dark (18L:6D). Lengthening photoperiod successfully rescued the fluorescent level of mitfa in zebrafish epidermis and most gene expressions associated with melanin synthesis under 25 μg/L BDE-47 exposure to the normal level. In conclusion, our work reported the effects of low-level PBDEs on melanin production using zebrafish embryos and larvae, and identified the potential role of a light-mediated pathway in the neurotoxic mechanism of PBDEs.

Comparative evaluation and prioritization of key influences on biodegradation of 2,2′,4,4′-tetrabrominated diphenyl ether by bacterial isolate B. xenovorans LB400

Polybrominated diphenyl ethers (PBDEs) are a class of persistent organic pollutants being widely distributed and harmful to human health and wildlife, and the development of sustainable rehabilitation strategies including microbial degradation is of great concern. Although the increasing number of bacteria, especially the broad-spectrum and potent aerobes have been isolated for the efficient removal of PBDEs, the external influences and the corresponding influential mechanism on biodegradation are not fully understood yet. Given the wide-spectrum biodegradability of aerobic bacterial isolate, B. xenovorans LB400 for PBDEs, the dual impacts of many pivotal factors including pH, temperature, presence of dissolved organic matter (DOM) and cadmium ion etc. were comprehensively revealed on biodegradation of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47). Due to the structural resemblance and stimulation of specific enzyme activity in bacteria, the biphenyl as substrates showed the greater capacity than non-aromatic compounds in improving biodegradation. The individual adaptation to neutrality and cultivation at about 30 °C was beneficial for biodegradation since the bacterial cellular viability and enzyme activity was mostly preserved. Although it was possibly good for the induction of hormesis and favorable to enhance the permeability or bioavailability of pollutant, the exceeding increase of Cd2+ or DOM may not give the profitable increase of biodegradation yet for the detrimental effect. For biodegradation, the mechanistic relationship that took account of the integrative correlation with the influential factors was artfully developed using partial least square (PLS) regression technique. Relative to the most significant influence of culture time and initial concentration of BDE-47, the larger relevance of other factors primarily marked as pH and DOM was consecutively shown after the quantitative prioritization. This may not only help understand the influential mechanism but provide a prioritizing regulation strategy for biodegradation of BDE-47. The PLS-derived relationship was validated with the certain predictability in biodegradation, and could be used as an alternative to accelerate a priori evaluation of suitability or improve the feasibility of such bacteria in remediation of PBDEs in the environment.

Integrated toxicology, metabolomics, and transcriptomics analyses reveal the biodegradation and adaptation mechanisms to BDE-47 in Pseudomonas plecoglossicida

Microbial degradation technology is often considered as an eco-friendly and cost-effective strategy to reduce the risks of 2,2′,4,4′-tetrabrominated diphenyl ether (BDE-47). However, the number of available BDE-47-degradating bacteria is insufficient, and there has yet to fully understand the biotransformation mechanisms of BDE-47. Here, a new strain, P. plecoglossicida, was isolated for the BDE-47 degradation. The biodegradation and adaption mechanisms of P. plecoglossicida to BDE-47 were systematically examined through an integrative approach combining toxicological assessment, degradation product analysis, metabolomic analysis, and transcriptomic analysis. Toxicological assessment and metabolomic analysis indicated that the adaptation mechanism of P. plecoglossicida to BDE-47 was mainly activating the antioxidant defense system to relieve the oxidative stress induced by BDE-47. However, the defense ability of P. plecoglossicida against BDE-47 was limited, and the high concentration of BDE-47 would result in the disturbance of amino acid and purine metabolism, and ultimately apoptosis. The analysis of degradation products and transcriptomics revealed that BDE-47 underwent debromination, hydroxylation, ether bond breaking, and ring-opening cleavage with the participation of multiple intracellular oxidoreductases. Besides, active efflux of BDE-47 and its degradation products mediated by efflux pump and multiple transporters might contribute to the bacterial tolerance against them. These results provided greater insights into the mechanisms of BDE-47 biodegradation.

Analysis of the functional gene of degrading BDE-47 by Acinetobacter pittii GB-2 based on transcriptome sequencing

2,2′,4,4′-tetrabrominated diphenyl ether (BDE-47) is one of the most widely distributed PBDEs. BDE-47 is also the most abundant in organisms and the most toxic to humans and animals. Herein, we have studied the pathway of BDE-47 degradation and gene involvement in Acinetobacter pittii GB-2. This degradation is dominated by hydroxylation, resulting in hydroxylated products 6-OH-BDE-47, 5-OH-BDE-47 and 2′-OH-BDE-28, and bromophenol products 2,4-DBP and 4-BP. Transcriptome sequencing results showed 359 differentially expressed genes (DEGs) induced by BDE-47, of which 159 were up-regulated and 200 were down-regulated. The up-regulated ones were mainly related to substance transport, degradation and cell stress. From these results, we suggest that 1,2-dioxygenase, phenol hydroxylase and monooxygenase are involved in BDE-47 degradation. The function of AntA gene was identified by constructing a prokaryotic expression vector. Our study contributes to understanding how the metabolism of strain GB-2 changes under BDE-47 stress conditions, and sheds light on the mechanism of BDE-47 degradation.

A cleanup method of serum extracts with molecular sieves as SPE sorbents for the analysis of polybrominated diphenyl ethers.

Based on the size- and shape-selective sorption, 13X molecular sieves were developed as solid-phase extraction adsorbents to cleanup serum extract for the determination of polybrominated diphenyl ethers. The important parameters affecting the cleanup efficiency were investigated including the amount of sorbents, the type, and volume of solvents. Under the optimized conditions, the capacity for removing impurities was evaluated via gel permeation chromatography and gas chromatography with mass spectrometry. The results demonstrated that up to 99% of lipids in corn oil (13 mg) can be removed after cleanup, and endogenous compounds in serum can also be effectively eliminated. The cleanup efficiency is not only superior to hydrophile-lipophile balance column, but also close to acid silica gel and multifunction impurity sorbents. Generally, the developed cleanup method exhibited higher recovery for polybrominated diphenyl ethers with more than four bromines, especially for nona- and deca-brominated diphenyl ethers (99.1-117.8%). The cleanup method can be coupled with gas chromatography and tandem mass spectrometry for polybrominated diphenyl ethers analysis in human serum. The method detection limits were 0.01-0.27 ng/mL and average recovery was 50.9-113.3%, except 2,3',4',6-tetrabrominated, 2,3',4,4',6-pentabrominated, and 2,3,3',4,4',5',6-heptabrominated diphenyl ethers. 2,2',4,5'-Tetrabrominated diphenyl ethers had the highest detection frequency (95%) in human serum, whereas decabrominated diphenyl ethers had the maximum mean concentration (0.50 ng/mL).

Microbial Debromination of Polybrominated Diphenyl Ethers by Dehalococcoides-Containing Enrichment Culture.

Polybrominated diphenyl ethers (PBDEs), commonly used as flame retardants in a wide variety of consumer products, are emerging persistent pollutants and ubiquitously distributed in the environment. The lack of proper bacterial populations to detoxify these recalcitrant pollutants, in particular of higher brominated congeners, has confounded the attempts to bioremediate PBDE-contaminated sites. In this study, we report a Dehalococcoides-containing enrichment culture, PB, which completely debrominates 0.44 μM tetra-brominated diphenyl ether (BDE) 47 to diphenyl ether within 25 days (0.07 μM Br–/day) and extensively debrominates 62.4 ± 4.5% of 0.34 μM hepta-BDE 183 (0.006 μM Br–/day) with a predominant generation of penta- through tri-BDEs as well as small amounts of diphenyl ether within 120 days. Later, a marked acceleration rate (0.021 μM Br–/day) and more extensive debromination (87.7 ± 2.1%) of 0.38 μM hepta-BDE 183 was observed in the presence of 0.44 μM tetra-BDE 47, which is achieved via the faster growth rate of responsible bacterial populations on lower BDE-47 and debromination by expressed BDE-47 reductive dehalogenases. Therefore, the PB enrichment culture can serve as a potential candidate for in situ PBDE bioremediation since both BDE-47 and BDE-183 are dominant and representative BDE congeners and often coexist in contaminated sites.

Degradation 2,2',4,4'-Tetrabromodiphenyl Ether by Activated Peroxymonosulfate Using Magnetic Biochar Supported α-MnO2

Polybrominated diphenyl ethers(PBDEs) are potentially harmful to human health and the ecological environment. It is, therefore, of great significance to develop efficient, economic, and environmentally-friendly advanced oxidation systems for their effective degradation. Here, a magnetic biochar supported manganese dioxide composite(α-MnO2/MWB) synthesized by hydrothermal methods was used as a catalyst to activate peroxymonosulfate(PMS) in the degradation of 2, 2', 4, 4'-tetrabrominated diphenyl ether(BDE-47). The prepared materials were characterized by SEM, XRD, FT-IR, and BET. The results showed that α-MnO2/MWB had the best catalytic performance, and the highest degradation efficiency reached 94% under optimal conditions(α-MnO2/MWB mass ratio=1:2, catalyst dosage=0.05 g·L-1, PMS concentration=5 mmol·L-1, BDE-47 concentration=1 mg·L-1). The effect of initial pH on the system was not distinct, while chloride ions(Cl-) and humic acid(HA) inhibited the degradation of BDE-47. In comparison, nitrate ions(NO3-) and bicarbonate ions(HCO3-) had no notable effect on the degradation. SO4-· and·OH were the key free radicals in the degradation of BDE-47 in this system, with SO4-· being dominant. As showed by the XPS characterization of the materials before and after the reaction, a change in the valence states of Mn and Fe was the main reason for the activation of PMS. It was also revealed that α-MnO2/MWB composites maintained high catalytic performance after being reused up to four times.

Identification of Reductive Dehalogenases That Mediate Complete Debromination of Penta- and Tetrabrominated Diphenyl Ethers in Dehalococcoides spp.

Polybrominated diphenyl ethers (PBDEs) are persistent, highly toxic, and widely distributed environmental pollutants. The microbial populations and functional reductive dehalogenases (RDases) responsible for PBDE debromination in anoxic systems remain poorly understood, which confounds bioremediation of PBDE-contaminated sites. Here, we report a PBDE-debrominating enrichment culture dominated by a previously undescribed Dehalococcoides mccartyi population. A D. mccartyi strain, designated TZ50, whose genome contains 25 putative RDase-encoding genes, was isolated from the debrominating enrichment culture. Strain TZ50 dehalogenated a mixture of pentabrominated diphenyl ether (penta-BDE) and tetra-BDE congeners (total BDEs, 1.48 μM) to diphenyl ether within 2 weeks (0.58 μM Br-/day) via ortho- and meta-bromine elimination; strain TZ50 also dechlorinated tetrachloroethene (PCE) to vinyl chloride and ethene (260.2 μM Cl-/day). Results of native PAGE, proteomic profiling, and in vitro enzymatic activity assays implicated the involvement of three RDases in PBDE and PCE dehalogenation. TZ50_0172 (PteATZ50) and TZ50_1083 (TceATZ50) were responsible for the debromination of penta- and tetra-BDEs to di-BDE. TZ50_0172 and TZ50_1083 were also implicated in the dechlorination of PCE to trichloroethene (TCE) and of TCE to vinyl chloride/ethene, respectively. The other expressed RDase, TZ50_0090 (designated BdeA), was associated with the debromination of di-BDE to diphenyl ether, but its role in PCE dechlorination was unclear. Comparatively few RDases are known to be involved in PBDE debromination, and the identification of PteATZ50, TceATZ50, and BdeA provides additional information for evaluating debromination potential at contaminated sites. Moreover, the ability of PteATZ50 and TceATZ50 to dehalogenate both PBDEs and PCE makes strain TZ50 a suitable candidate for the remediation of cocontaminated sites. IMPORTANCE The ubiquity, toxicity, and persistence of polybrominated diphenyl ethers (PBDEs) in the environment have drawn significant public and scientific interest to the need for the remediation of PBDE-contaminated ecosystems. However, the low bioavailability of PBDEs in environmental compartments typically limits bioremediation of PBDEs and has long impeded the study of anaerobic microbial PBDE removal. In the current study, a novel Dehalococcoides mccartyi strain, dubbed strain TZ50, that expresses RDases that mediate organohalide respiration of both PBDEs and chloroethenes was isolated and characterized. Strain TZ50 could potentially be used to remediate multiple cooccurring organohalides in contaminated systems.

Effects of methanol on the performance of a novel BDE-47 degrading bacterial consortium QY2 in the co-metabolism process

2,2′,4,4′-tetrabrominated diphenyl ether (BDE-47), frequently detected in the environment, is arduous to be removed by conventional biological treatments due to its persistence and toxicity. Herein effects of methanol as a co-metabolic substrate on the biodegradation of BDE-47 was systematically studied by a functional bacterial consortium QY2, constructed through long-term and successive acclimation from indigenous microorganisms. The results revealed that BDE-47 (0.25 mg/L) was completely removed within 7 days in the 2.5 mM methanol treatment group, and its degradation efficiency was 3.26 times higher than that without methanol treatment. The addition of methanol dramatically accelerated the debromination, hydroxylation and phenyl ether bond breakage of BDE-47 by QY2. However, excessive methanol (>5 mM) combined with BDE-47 had strong stress on microbial cells, including significant (p < 0.05) increase of reactive oxygen species level, superoxide dismutase activity, catalase activity and malondialdehyde content, even causing 20.65% cell apoptosis and 11.27% death. It was worth noting that the changes of QY2 community structure remained relatively stable after adding methanol, presumably attributed to the important role of the genus Methylobacterium in maintaining the functional and structural stability of QY2. This study deepened our understanding of how methanol as co-metabolite substances stimulated the biodegradation of BDE-47 by microbial consortium.

Transcriptome profiling of Pseudomonas aeruginosa YH reveals mechanisms of 2, 2′, 4, 4′-tetrabrominated diphenyl ether tolerance and biotransformation

Aerobic degradation of 2, 2′, 4, 4′-tetrabrominated diphenyl ether (BDE-47) by Pseudomonas aeruginosa YH (P. aeruginosa YH) were investigated in this study. BDE-47 degradation was mainly through the biological action of intracellular enzymes, and the metabolites included debrominated metabolites (BDE-28 and BDE-7), hydroxylated metabolites (6-OH-BDE-47, 5-OH-BDE-47, 2′-OH-BDE-28 and 4′-OH-BDE-17), and brominated phenols (2,4-DBP and 4-BP). P. aeruginosa YH also exhibited exceptional ability to degrade intermediates, and the degradation rates of 50 μg/L BDE-28, BDE-7, and 2,4-DBP were 68.4%, 82.3% and 92.7% on the 5th day, separately. Transcriptome sequencing revealed that 991 genes were up-regulated, and 923 genes were down-regulated in P. aeruginosa YH after exposure to 0.5 mg/L BDE-47 (FDR ≤ 0.001, |log2Ratio| ≥ 1). The differentially expressed genes were related to transport, metabolism and stress response. Harf inhibitory concentration (IC50) of BDE-47 decreased from 167.5 mg/L to 68.4 mg/L when multidrug efflux pump was inactivated by 20 mg/L andrographolide, indicating that it helped the bacterial tolerance against BDE-47. Moreover, efflux pump inhibition would accelerate the adsorption of BDE-47. The adsorption rate obtained equilibrium at approximately 70% in 2 days, while 5 days in the control group. Degradation efficiency of 2 mg/L BDE-47 decreased from 26.8% to 13.9% when multidrug efflux was suppressed.

Degradation of 2, 2′, 4, 4′-Tetrabrominated diphenyl ether (BDE-47) via the Fenton reaction driven by the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1

A microbially facilitated approach was developed to degrade 2, 2′, 4, 4′-tetrabrominated diphenyl ether (BDE-47). This approach consisted of biological production of Fe(II) and H2O2 by the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 during the repetitive anoxic/oxic cycles and abiotic production of hydroxyl radical (HO●) with the biologically produced Fe(II) and H2O2 via Fenton reaction. Under the condition tested, BDE-47 did not inhibit the growth of S. oneidensis MR-1. Water soluble Fe(III)-citrate and the solid minerals ferrihydrite [Fe(III)2O3•0.5H2O] and goethite [Fe(III)OOH] were tested in this study. Under anoxic condition, the amounts of Fe(II) produced by S. oneidensis MR-1 varied among the Fe(III)s tested, which decreased in the order of Fe(III)-citrate > ferrihydrite > goethite. Under subsequent oxic condition, H2O2 was produced via O2 reduction by S. oneidensis MR-1. The amounts of H2O2 detected also varied, which decreased in the order of the reactions with Fe(III)-citrate > goethite > ferrihydrite. S. oneidensis MR-1 maintained its ability to produce Fe(II) and H2O2 for up to seven anoxic/oxic cycles. At each end of anoxic/oxic cycle, HO● was detected. The amount of HO● produced decreased in the order of the reactions with ferrihydrite > goethite > Fe(III)-citrate, which was opposite to that of H2O2 detected. Compared to the controls without HO●, the amounts of BDE-47 in the reactions with HO● decreased. The more HO● in the reaction, the less amount of BDE-47 detected. Furthermore, no BDE-47 degradation was observed when HO● was scavenged or ferrihydrite was either omitted or replaced by nitrate. Finally, identification of degradation products, such as hydroxylated BDE-47 and trisBDE, dibromophenol and monobromophenol, suggested that OH-addition and Br-substitution by HO● were the main mechanisms for degrading BDE-47. Collectively, all these results demonstrated for the first time that the Fenton reaction driven by S. oneidensis MR-1 degraded BDE-47 effectively.

Hepatic oxidative stress, DNA damage and apoptosis in adult zebrafish following sub-chronic exposure to BDE-47 and BDE-153.

Polybrominated diphenyl ethers (PBDEs) are ubiquitous and prolific contaminant in both the abiotic and biotic environment because of the wide industrial applications of these chemicals. In the present study, the effects of 2,2',4,4'-tetrabrominateddiphenyl ether (BDE-47) and 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE-153) exposure on the induction of hepatic oxidative stress, DNA damage, and the expression of apoptosis-related genes in adult zebrafish were investigated. The activities of antioxidant enzymes, such as catalase and superoxide dimutase, significantly increased when adult zebrafish was exposed to various concentrations of BDE-47 and BDE-153 for 7 and 15 days. BDE-47 and BDE-153 elicited significant alterations in zebrafish 7-Ethoxyresorufin-O-deethylase activity at 3, 7, or 15 days of exposure. In addition, the significant increase in comet assay parameters of zebrafish hepatocytes in a concentration-dependent manner indicated BDE-47 and BDE-153 induced DNA damage, probably due to observed oxidative stress. Furthermore, a monotonically upregulation of p53 and Caspase3, which are apoptotic-regulated genes, and decreased expression ratio of the anti-apoptotic B-cell lymphoma/leukaemia-2 and Bcl2-associated X protein genes for all BDE-47 and BDE-153 treatments at 7 and 15 days indicated apoptosis induction in zebrafish liver. Our findings help elucidate the mechanisms of BDE-47- and BDE-153-induced toxicity in zebrafish hepatocytes.

Photoassisted degradation of 2,2′,4,4′-tetrabrominated diphenyl ether in simulated soil washing system containing Triton X series surfactants

This study aims to use ultraviolet (UV) irradiation to decompose polybrominated diphenyl ethers (PBDEs) in the elutes and then reuse the surfactants. The results indicate that UV can remove 2,2′,4,4′-tetrabrominated diphenyl ether (BDE-47) from surfactant eluents and Triton X series surfactants also can remove BDE-47 from the soil. Triton X-100 (TX-100) is the most promising surfactant during the washing and photodegradation processes. Quench experiments suggest that both 1O2 and OH• were involved in the TX-100 decomposition but only 1O2 is responsible for the degradation of BDE-47. In analysis of the photoproducts of BDE-47 by Gas Chromatography Mass Spectrum (GC-MS) and Liquid Chromatography High Resolution Mass Spectrometry (LC-HRMS), BDE-47 was mainly debrominated to the lower-brominated BDEs and then oxidized to ring-opening products. The little loss of TX-100 can mainly be attributed to the breakage of polyethylene oxide (PEO) chain. Nevertheless, the washing wastes treated by UV light can exhibit higher solubility for BDE-47 than before, indicating they can be reused for BDE-47 removal from soil. The toxicity assessment experiments were performed using Escherichia coli (E.coli) as an indicator. The results indicate that the removal of BDE-47 by UV irradiation can reduce the toxicity of eluent.

Exposure to PBDE47 affects mouse oocyte quality via mitochondria dysfunction-induced oxidative stress and apoptosis.

2, 2', 4, 4'-Tetrabrominated diphenyl ether (PBDE47) is the most abundant homologues in polybrominated diphenyl ethers (PBDEs) and is used widely in daily life as a brominated flame retardant. It has been shown that PBDE47 has neurotoxicity, thyroid toxicity, and also is reported to have reproductive toxicity, which can impair the follicular function of female rats and activate ovarian endoplasmic reticulum stress, leading to ovarian damage. However, the toxicity of PBDE47 to the quality of mammalian oocyte has not been reported. In this study, we reported that PBDE47 exposure affected the mouse ovarian and uterine. We also showed that oocyte number reduced and meiotic maturation competence decreased. Moreover, PBDE47 exposure disrupted actin filaments distribution, and also changed the level of histone methylation. Based on the genome-wide sequencing we showed that PBDE47 altered multiple gene expression in mouse oocytes. PBDE47 exposure caused mitochondria dysfunction, showing with aberrant distribution and mitochondrial membrane potential. In addition, our results suggested that PBDE47 induced early apoptosis, which was caused by oxidative stress, showing with increased ROS level and positive Annexin-V signal. In conclusion, our results indicated that PBDE47 exposure affected the maturation of mouse oocyte via its effects on mitochondria function, ROS level and its related apoptosis.

Accumulation and Transformation of 2,2',4,4'-Tetrabrominated Diphenyl Ether (BDE47) by the Earthworm Metaphire vulgaris in Soil.

The accumulation and transformation of 2,2',4,4'-tetrabrominated diphenyl ether (BDE47), one congener of the flame retardants polybrominated diphenyl ethers (PBDEs), in soil-feeding fauna are still unknown. Using radioactivity tracer, we incubated 14C-labelled BDE47 in soil for 21 days in the presence and absence of the geophagous earthworm Metaphire vulgaris. BDE47 accumulated in the earthworm predominantly via oral ingestion of soil, giving a biota-soil accumulation factor (BSAF) value of 1.3 for radioactivity at the end of incubation, and was mostly located in intestine, followed by clitellum (organs region) and skin of earthworms. Accumulation was accompanied by significant decrease of BDE47 concentration in soil porewater and BDE47 mineralization in soil. BDE47 was transformed in the earthworm gut into two metabolites with higher polarities than BDE47. The results provide for the first time insights into accumulation and transformation of lower-brominated congeners of PBDEs in geophagous earthworms, being helpful for environmental risk assessment of PBDEs.

Understanding the role of bacterial cellular adsorption, accumulation and bioavailability regulation by biosurfactant in affecting biodegradation efficacy of polybrominated diphenyl ethers

Microbiological degradation is often considered as an important strategy to reduce the risks of polybrominated diphenyl ethers (PBDEs), which are environmentally widespread and harmful to human health and wildlife. With the well-identified aerobic bacteria, i.e. B. xenovorans LB400, the biodegradation of 2,2′,4,4′-tetrabrominated diphenyl ether (BDE-47) occurred efficiently in conformity to the first-order kinetics and showed the strong dependence on initial concentration of pollutant and bioavailability regulation by biosurfactant. The mild increase of initial concentration of BDE-47 would enhance biodegradation whereas the excessive increase failed due to the oxidative stress or cytotoxicity to bacteria. Rather than the bacterial extracellular adsorption that was bioactively-mediated in thermodynamics, the intracellular accumulations at different time gradients showed the negative correlation with biodegradation efficiency of BDE-47. The spontaneous biodegradation of pollutant should be sourced from the gradual reduction of intracellular accumulation. Though the improved bioavailability of BDE-47 by sucrose fatty acid ester (SFAE) hardly altered the extracellular adsorption, the bacterial intracellular accumulation was indicated to increase continuously with used amount of biosurfactant and then decrease for the cellular morphological damage, and interestingly it appeared to be temporary reservoir for prompt delivery to biodegradation in light of the opposite variation tendency with time.

Biochar combined with compost to reduce the mobility, bioavailability and plant uptake of 2,2',4,4'-tetrabrominated diphenyl ether in soil.

Biochar application to soil is recognised for its capacity to immobilise pollutants (through sorption) while composted inputs can accelerate the biodegradation of organic pollutants. However, little is known about the influence of combined incorporation on plant uptake of organic pollutants. Therefore, we investigated the effects of maize straw-derived biochar (MSB), compost derived from maize straw and pig manure (SMC), and their combination (MSB-SMC) as soil amendments on bioavailability of 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) and carrot (Daucus carota L.) uptake in a horticultural soil. We found that biochar alone performed well in reducing BDE-47 bioavailability, but was less effective at degrading the pollutant. Conversely, addition of compost stimulated BDE-47 biodegradation. MSB-SMC enhanced BDE-47 biodegradation in soil, reduced contamination of carrot roots, and caused significant reductions in soil extractable BDE-47. The combination of contrasting approaches to remediation thus resulted in the most favorable outcome for a contaminated soil: immobilisation of contaminant from vegetable crops (via biochar) with simultaneous bioremediation of the growing medium. These findings point towards an effective strategy for reducing plant uptake of PDBEs through the combined use of biochar and compost as soil amendment - reducing mobility and facilitating degradation of the accessible contaminant fractions.