Although the abiotic and biotic transformation/degradation (T/D) processes of tetrabromobisphenol A (TBBPA) have been widely investigated in model experiments, few reviews have focused on these ...processes along with their metabolites or degradation products. In this paper, we summarize the current knowledge on the T/D of TBBPA and its derivatives, including abiotic and biotic T/D strategies/conditions, mechanisms, metabolites and environmental occurrences. Various treatments, such as pyrolysis, photolysis, chemical reactions and biotransformation, have been employed to study the metabolic mechanism of TBBPA and its derivatives and to remediate associated contaminated environments. To date, more than 100 degradation products and metabolites have been identified, dominated by less brominated compounds such as bisphenol A, 2,6-dibromo-4-isopropylphenol, 2,6-dibromo-4-hydroxyl-phenol, 2,6-dibromophenol, isopropylene-2,6-dibromophenol, 4-(2-hydroxyisopropyl)-2,6-dibromophenol, etc. It can be concluded that the T/D of TBBPA mainly takes place through debromination and β-scission. In some environmental media and human and animal tissues, brominated metabolites, glucoside and sulfate derivatives are also important T/D products. Here, the T/D products of TBBPA and its derivatives have been most comprehensively presented from the literature in recent 20 years. This review will enhance the understanding of the environmental behaviors of TBBPA-associated brominated flame retardants along with their ecological and health risks.
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•Transformation/degradation (T/D) of TBBPA is most comprehensively reviewed.•T/D is involved in thermo-treatment, chemical reaction, microbe, organism, etc.•Debromination and β-scission are the main T/D pathways.•More than 100 intermediates or metabolites have been identified in recent years.•Fate and risk of metabolites are rarely studied for the lack of purity standards.
T/D of TBBPA and its derivatives, including strategies/conditions, mechanism, metabolites and environmental occurrence is most systematically reviewed from the literature over the past 20 years.
Abstract
Nervonic acid benefits the treatment of neurological diseases and the health of brain. In this study, we employed the oleaginous yeast
Yarrowia lipolytica
to overproduce nervonic acid oil by ...systematic metabolic engineering. First, the production of nervonic acid was dramatically improved by iterative expression of the genes ecoding β-ketoacyl-CoA synthase
Cg
KCS, fatty acid elongase gELOVL6 and desaturase MaOLE2. Second, the biosynthesis of both nervonic acid and lipids were further enhanced by expression of glycerol-3-phosphate acyltransferases and diacylglycerol acyltransferases from
Malania oleifera
in endoplasmic reticulum (ER). Third, overexpression of a newly identified ER structure regulator gene
YlINO2
led to a 39.3% increase in lipid production. Fourth, disruption of the AMP-activated S/T protein kinase gene
SNF1
increased the ratio of nervonic acid to lignoceric acid by 61.6%. Next, pilot-scale fermentation using the strain YLNA9 exhibited a lipid titer of 96.7 g/L and a nervonic acid titer of 17.3 g/L (17.9% of total fatty acids), the highest reported titer to date. Finally, a proof-of-concept purification and separation of nervonic acid were performed and the purity of it reached 98.7%. This study suggested that oleaginous yeasts are attractive hosts for the cost-efficient production of nervonic acid and possibly other very long-chain fatty acids (VLCFAs).
The chemical industrial zone located along the Xiaoqing River wetlands adjacent to Bohai Sea is one of the largest production bases for brominated flame retardants in China. Herein, high levels of ...bisphenol-A, tetrabromobisphenol-A (TBBPA), tribromobisphenol-A, dibromobisphenol-A, and monobromobisphenol-A were detected in sediment, soil, and water samples of this zone in the range of below method detection limit (<MDL)–5.45 × 106 ng/kg dw, <MDL–8.37 × 104 ng/kg dw, and <MDL–5.59 × 102 ng/L, respectively. They were mainly buried in sediments as their highest levels in sediment samples. The small concentration fluctuation between water samples retrieved in the upstream and downstream zones is likely attributed to seawater backflow. The nearby chemical factories were point pollution sources and the less brominated analogs are largely from debromination of TBBPA. High pollution levels and the ecological risks of these pollutants along the Xiaoqing estuary to Bohai Sea need to be further assessed in future studies.
•BPA, TBBPA and analogs were detected along tributary of Xiaoqing River to Bohai Sea.•All these contaminants in water, soils and sediments presented much higher levels.•The nearby BFRs factories are attributed to pollution of TBBPA, BPA and analogs.•Large proportion of TriBBPA, DBBPA and MBBPA were from debromination of TBBPA.•TBBPA, BPA and analogs were delivered to Bohai Sea mainly by river inputs.
Compared with tetrabromobisphenol A (TBBPA) and its derivatives, the skeletally similar chemicals tetrabromobisphenol S (TBBPS) and its derivatives have been rarely studied, and very little is known ...about their structures, environmental occurrence, and behaviors. In this study, a total of 84 soil samples from a chemical industrial park have been collected and analyzed to investigate the occurrence of TBBPS and its derivatives and to identify novel TBBPS analogs. TBBPS, TBBPS bis(2,3-dibromopropyl ether) (TBBPS-BDBPE), and three byproducts, TBBPS mono(allyl ether) (TBBPS-MAE), TBBPS mono(2-bromoallyl ether) (TBBPS-MBAE), and TBBPS mono(2,3-dibromopropyl ether) (TBBPS-MDBPE), have been detected with contents ranging from below detection limits to 1934.6 ng/g dw and with detection frequencies of 21.4–97.6%. In addition, another 5 unknown TBBPS analogs, tribromobisphenol S (TriBBPS), 2,2′,6′-TriBBPS-MAE (TriBBPS-MAE3.2), 2,6,2′-TriBBPS-MAE (TriBBPS-MAE3.4), 2′,6′-DBBPS-MAE (DBBPS-MAE2.0), and 2,6-DBBPS-MAE (DBBPS-MAE2.6), have been identified in these soil samples by untargeted mass spectrometry screening. These unknown analogs have also been observed in laboratory transformation experiments of TBBPS-MDBPE conducted under reducing conditions. TriBBPS-MAE3.4 and DBBPS-MAE2.6 were more likely to be produced than TriBBPS-MAE3.2 and DBBPS-MAE2.0 due to the stereoselectivity of the transformation. TriBBPS-MAE3.4 and DBBPS-MAE2.0 were more stable, resulting in higher detection frequencies of these compounds in soil samples. Ether bond breakage and debromination contributed to the generation of these novel products. The results provide new information on the behaviors of TBBPS and its derivatives in the environment.
The structural identification as well as quantitative analysis of transformation and degradation (T/D) products of tetrabromobisphenol A (TBBPA) and its derivatives can provide useful information on ...the corresponding T/D mechanism as well as environmental impact. However, it is still a great challenge to analyze trace levels of T/D products, both unknown and known products, as a result of the complexity of environmental matrices and the lack of commercial/artificial standard chemicals. This critical review summarized the T/D model experiments, sample preparation and the associated analytical methods, including extraction, purification, concentration, derivatization, quantitation analysis and 14C-labeling technologies. Furthermore, the mass spectral analysis of TBBPA related compounds using different analytical instruments and T/D products predicted by computer programs are also described.
•Transformation/degradation (T/D) products were identified in model experiments.•Sample preparation and analytical methods of T/D products of TBBPA were reviewed.•Novel T/D products were based on spectra elucidation by different mass instruments.•Possible T/D products can be predicted by software.•Compared with TBBPA, T/D of TBBPA derivatives has not been well studies.
•A novel method was developed for five high production TBBPA/S and derivatives.•Thin-layer chromatography (TLC) was introduced for pretreatment of soil samples.•Both the qualitative and quantitative ...information were obtained with HPLC-DAD.•The method was rapid, convenient and cost-effective for complex sample depuration.
As brominated flame retardants (BFRs), tetrabromobisphenol A/S (TBBPA/S) and their derivatives have raised wide concerns owing to their widely usage, distributions and adverse effects on human health, thus monitoring these BFRs was urgently needed. In this study, a rapid and cost-effective method based on thin-layer chromatography (TLC) sample pre-treatment coupled with high performance liquid chromatography-diode array detector (HPLC-DAD) (UV=214nm) was developed for determining TBBPA/S and their derivatives in soils, including TBBPA, TBBPA bis(allyl ether) (TBBPA-BAE), TBBPA bis(2,3-dibromopropyl ether) (TBBPA-BDBPE), TBBPS bis(allyl ether) (TBBPS-BAE) and TBBPS bis(2,3-dibromopropyl ether) (TBBPS-BDBPE). The method detection limits (MDLs) and the method quantification limits (MQLs) for these BFRs ranged from 0.023 to 0.087μgg−1dw and 0.076–0.29μgg−1dw, respectively. The recoveries were 41–108% and both RSD of repeatability and intermediate precision were less than 11%. The developed method presented good performance for analyzing natural soil samples collected from BFRs industrial park, suggesting its great application potential for monitoring environmental TBBPA/S and their derivatives.
Bisphenol A (BPA) and its brominated analogs exhibiting bioaccumulation potential, endocrine disruption, and reproductive toxicity have been worldwide detected in water, air, soil, and sediments. But ...few methods have been proposed for simultaneously determining a variety of these compounds in biological matrices, hindering the further study on their biological transformation/degradation and health risks. In this study, a simple, solvent-saving and sensitive method based on high-performance thin-layer chromatography (HPTLC) for sample pretreatment coupled with high-performance liquid chromatography-diode array detector (HPLC-DAD) (UV = 214 nm)/triple quadrupole mass spectrometry (MS/MS) was developed for determining BPA and its nine brominated analogs in biological samples. The method detection limits (MDLs) and method quantification limits (MQLs) for ten BPA analogs ranged from 0.8 to 685.7 ng g
−1
dw (S/N = 3) and 2.7 to 2285.7 ng g
−1
dw (S/N = 10), respectively. The recoveries were 64–124% with SD less than 10%. The RSD of intermediate precision was less than 11%, and matrix effects were lower than 19%. Compared with traditional purification procedures, HPTLC largely reduced the workload and procedures for complex biological sample cleanup without inducing decomposition of the analytes. The proposed method exhibited good performance when detecting these ten chemicals in chicken samples from a nearby yard of brominated flame retardant plants, indicating its great potential for investigating their environment level, behavior, and fate in organisms.
Graphical abstract
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•The antioxidant activity of δ-viniferin and ε-viniferin is systematically examined.•Hydrogen atom transfer and radical adduct formation pathways are studied.•δ-viniferin exhibits stronger ...antioxidant activity than ε-viniferin.•The most reactive sites of δ-viniferin and ε-viniferin are 12-OH and 12′-OH.
As an important chemical component of grapes, viniferins are essential dimers of natural product resveratrol with good antioxidant activity. In this study, we have examined the antioxidant activity of two viniferin molecules (δ-viniferin and ε-viniferin) with ·OH/·OOH radicals. Density functional theory (DFT) calculations at the M062X/6–311++G(d,p)-SMD//M062X/6–311G(d,p) level of theory in the gas phase, water, and benzene used to examine two crucial radical scavenging pathways: hydrogen atom transfer (HAT) and the radical adduct formation (RAF). Then, the radical scavenging activities of the two molecules are compared kinetically and thermodynamically. The Gibbs free energy of activation (ΔG≠) and rate constant (kTST) are calculated using the conventional transition state theory (TST), and the results reveal that HAT and RAF processes compete in different solvents. Furthermore, molecular electrostatic potential (MEP) and frontier molecular orbital (FMO) of both the compounds are computed to elucidate their antioxidant activity. The results show that the RAF site appears at the >C7C8< double bond position of δ- and ε-viniferins, and the most favorable HAT positions of δ-viniferin and ε-viniferin are 12′-OH and 12-OH, respectively; in addition, ε-viniferin is a more potent radical scavenging agent than δ-viniferin. These findings provide useful insights on the antioxidant activity of viniferins and different radical scavenging mechanisms of antioxidants, which can be beneficial for improving the practical utilization of resveratrol dimer and other analogs.
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Electricity load forecasting is an essential, however complicated work. Due to the influence of a large number of uncertain factors, it shows complicated nonlinear combination features. Therefore, it ...is difficult to improve the prediction accuracy and the tremendous breadth of applicability especially for using a single method. In order to improve the performance including accuracy and applicability of electricity load forecasting, in this paper, a concept named minimum cycle decomposition (MCD) that the raw data are grouped according to the minimum cycle was proposed for the first time. In addition, a hybrid prediction model (HMM) based on one-order difference, ensemble empirical model decomposition (EEMD), mind evolutionary computation (MEC) and wavelet neural network (WNN) was also proposed in this study. The HMM model consists of two parts. Part one, pre-processing, known as one order difference to remove the trend of subsequence and EEMD to reduce the noise, was performed by HMM model on each subset. Part two, the WNN optimized by MEC (WNN
+
MEC) was applied on resultant subseries. Finally, a number of different models were used as the comparative experiment to validate the effectiveness of the presented method, such as back propagation neural network (BP-1), BPNN combined MCD (BP-2), WNN combined MCD (WNNM), a HMM (DEEPLSSVM) based on one-order difference, EEMD, particle swarm optimization and least squares support vector machine and a hybrid model (DEESGRNN) based on one-order difference, EEMD, simulate anneal and generalized regression neural network. Certain evaluation measurements are taken into account to assess the performance. Experiments were carried out on QLD (Queensland) and NSW (New South Wales) electricity markets historical data, and the experimental results show that the MCD has the advantages of improving model accuracy and of generalization ability. In addition, the simulation results also suggested that the proposed hybrid model has better performance.
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