High-level production of nervonic acid in the oleaginous yeast Yarrowia lipolytica by systematic metabolic engineering.

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 ß-ketoacyl-CoA synthase CgKCS, 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).

Occurrence of bisphenol-A and its brominated derivatives in tributary and estuary of Xiaoqing River adjacent to Bohai Sea, China.

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 (

High-performance thin-layer chromatography coupled with HPLC-DAD/HPLC-MS/MS for simultaneous determination of bisphenol A and nine brominated analogs in biological samples.

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 ᅟ.

Transformation/degradation of tetrabromobisphenol A and its derivatives: A review of the metabolism and metabolites.

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 ß-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.

Identification of Unknown Brominated Bisphenol S Congeners in Contaminated Soils as the Transformation Products of Tetrabromobisphenol S Derivatives.

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.

Thin-layer chromatography coupled with high performance liquid chromatography for determining tetrabromobisphenol A/S and their derivatives in soils.

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.