Short-chain Carboxylic Acids Research Articles

Integration of anaerobic digestion and chain elongation technologies for biogas and carboxylic acids production from cheese whey

Cheese whey (CW) used for the production of various chemicals in different studies, but no studies designed to produce multiple energy in the form of short-chain/medium-chain carboxylic acids, and biohydrogen (H2) using bio-augmentation strategy by integrating the anaerobic digestion and chain elongation technologies. To achieve this, CW and mixed anaerobic bacteria were kept in an anaerobic chamber for 14 d to produce short chain carboxylic acids (SCCA, acetic (C2), propionic (C3), and butyric (C4) acids), and these SCCA were again converted to medium chain carboxylic acids (MCCA) like hexanoic (C6), heptanoic (C7), and octanoic (C8) acids using enriched bacterial culture, which was bio-augmented with Clostridium kluyveri. SCCA, MCCA, and biogas were analyzed with HPLC and GC. Higher amounts of SCCA, i.e., C2 (10 g/L), C4 (8.1 g/L), and MCCA, i.e., C6 (4.8 g/L), were produced. Biohydrogen (H2) existed in the highest proposition (69%) in biogas composition. Results meant that bio-augmentation strategy could be used for the conversion of CW into valuable carboxylic acids and H2, which have high potential in today's market.

Occurrence, distribution, and input pathways of per- and polyfluoroalkyl substances in soils near different sources in Shanghai

Per- and polyfluoroalkyl substances (PFAS) are complex emerging pollutants that are widely distributed in soils. The compositions of PFAS vary according to the emission sources. However, the soil distributions of PFAS from different sources are still poorly understood. In this study, the concentrations and compositions of 18 PFAS in soils close to potential sources (industrial areas, airports, landfills, fire stations and agricultural areas) were investigated in Shanghai. The total PFAS concentrations varied from 0.64 to 294 μg kg−1d.w.. Among the sites, the highest PFAS concentration was found near the fire station (average = 57.9 μg kg−1d.w.), followed by the industrial area (average = 8.53 μg kg−1d.w.). The detection frequencies of the 18 PFAS ranged from 47.5% to 100%. Perfluorooctanoic acid (PFOA) and perfluoroheptanoic acid (PFHpA) were detected in all samples. The detection frequencies of PFAS near the fire station were higher than those near other sources. The PFAS in soils were mainly composed of short-chain perfluoroalkyl carboxylic acids (C ≤ 8). Elevated concentrations of long-chain perfluoroalkyl carboxylic acids (C > 12) were found in industrial area. Principal component analysis revealed that long-chain PFAS had different factor loadings compared to short-chain PFAS. With the exception of agricultural soils, the correlations between individual PFAS were more positive than negative. Strong positive correlations were found within three groups of perfluoroalkyl carboxylic acids (C5–C7, C9–C12, and C14–C18), suggesting their similar inputs and transportation pathways. The PFAS in soils around the fire station were likely directly emitted from a point source. In contrast, the PFAS in soils near the other sites had multiple input pathways, including both direct emission and precursor degradation.

New development of a solar electrochemical raceway pond reactor for industrial wastewater treatment

In this work, a solar electrochemical-raceway pond reactor (SEC-RPR) is used to treat textile industrial wastewater by solar photoelectron-Fenton (SPEF) at pilot plant scale for the first time. The SEC-RPR is composed of an electrochemical filter press-cell coupled to RPR, where H2O2 is electro-generated. A complete study about experimental variables such as current, catalyst concentration, pollutant load or liquid depth is conducted based on methyl orange removal, mineralization and decolorization. Validation of the SPEF process using SEC-RPR reached more than 80% of mineralization, as well as the complete decolorization of the solution. The good performance of the SPEF treatment in the new SEC-RPR led to quick degradation kinetics, mainly due to the synergetic action of solar radiation and good distribution of H2O2 electrogenerated in the photoreactor. 100% Methyl Orange degradation was achieved after 150, 60, 45, 30 and 20 min of reaction time applying current density equal to 5, 10, 20, 40 and 60 mA cm−2, respectively. However, the increase of current density decreased the mineralization current efficiency. Up to 10 aromatics intermediates and 5 short-chain carboxylic acids were identified by LC-MS and HPLC analysis and a reaction pathway for MO mineralization by SPEF is proposed. This study represents an essential preliminary step towards the development of the first SEC-RPR at demo scale.

Emerging and Legacy Per- and Polyfluoroalkyl Substances in an Elderly Population in Jinan, China: The Exposure Level, Short-Term Variation, and Intake Assessment.

Human exposure to per- and polyfluoroalkyl substances (PFASs) has gained worldwide attention due to their widespread presence in the environment and adverse health effects, but the exposure assessment in the elderly is still lacking. This study aimed to assess exposures to 3 emerging PFASs (chlorinated polyfluoroalkyl ether sulfonic acids, Cl-PFESAs) and 15 legacy PFASs. The temporal variability of internal exposures and intake amounts of these PFASs were evaluated among a population of 76 healthy elderly adults (age: 60-69) in Jinan, China over 5 consecutive months. Fifteen PFASs were detected in whole blood with the mean total concentration (ΣPFAS) at 20.1 ng/mL (range: 5.0-135.9 ng/mL) dominated by perfluorooctanoic acid (PFOA) (9.0 ng/mL), perfluorooctanesulfonic acid (PFOS) (5.3 ng/mL), and 6:2 Cl-PFESA (1.6 ng/mL). Across the 5 month assessment period, significant variation was only observed for short-chain (C4-C7) perfluoroalkyl carboxylic acids, and their variations ranged from 53 to 334%. The median intake of PFOA and PFOS was estimated to be 1.46 and 0.92 ng/kg bw/day, respectively. Regression analysis showed that dietary ingestion, especially fish, was likely an important exposure pathway for PFASs among the elderly adults. Various pathways (e.g., dietary, water, air, and dust) should thus be considered to fully understand human exposure to PFASs.

Degradation of cefadroxil by photoelectrocatalytic ozonation under visible-light irradiation and single processes

Here, we investigate the degradation of 20 mg L-1 Cefadroxil (CFX) in water using photoelectrocatalytic ozonation (PECO), and compared against its individual processes. A carbon nitrogen-codoped titanium dioxide (CN-TiO2) anode is synthesized using ethylene glycol and ethylenediamine as carbon and nitrogen source, respectively. The X-ray diffraction (XRD) and Scanning Electronic Microscopy (SEM) analysis conducted to this material indicate a crystalline phase anatase with irregular morphology formed on the electrode surface; while the diffuse reflectance spectroscopy (DRS) shows a shift in the photoanode absorbance towards the visible region, unlike undoped TiO2 structure. This behavior results from the inclusion of Carbon and Nitrogen species on the CN-TiO2 electrode in weight percentages of 14.5 and 1.61 wt%, respectively, according to Energy Dispersive Spectroscopy (EDS) analysis. The Cefadroxil (CFX) abatement is monitored UV–Vis spectroscopy, high-performance liquid chromatography (HPLC), and total organic carbon (TOC). All techniques reveal that the highest CFX removal occurs with PECO (Photoelectrocatalytic Ozonation) process, decreasing TOC by 57.6% (96% degradation by HPLC) after 90 min of treatment. The main by-products formed from oxidation with the PECO, PCO (Photocatalytic Ozonation) and O3 (Ozonation) systems were acid species presumably corresponding to short chain carboxylic acids. Finally, the germination of lettuce sativa is carried out in water contaminated with the drug, and compared with water treated by PECO and PCO processes, showing that PECO process improves germination by 23.5% on the contaminated sample and 7.4% on the sample treated with PCO. These findings confirm that synergism of oxidation techniques could be a tractable way to resolve the problems related to recalcitrant compounds contained in wastewater.

Polyhydroxyalkanoates production from short and medium chain carboxylic acids by Paracoccus homiensis

The aim of this study was to evaluate an effect of short and medium chain carboxylic acids (CAs) rich stream derived from acidogenic mixed culture fermentation of acid whey on polyhydroxyalkanoates (PHAs) synthesis by Paracoccus homiensis and compare it with the impact of individual synthetic CAs. The obtained results confirmed that the analyzed bacterium is able to metabolize synthetic CAs as the only carbon sources in the growth medium with maximum PHAs production yields of 26% of cell dry mass (CDM). The replacement of the individual CAs by a CAs-rich residual stream was found to be beneficial for the Paracoccus homiensis growth. The highest biomass concentration reached about 2.5 g/L with PHAs content of 17% of CDM. The purified PHAs were identified as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by applying gas chromatography coupled with mass spectrometry, Fourier transform infrared spectroscopic spectra and UV–Vis spectra. Furthermore, a differential scanning calorimetric, thermogravimetric and water contact angle analysis proved that the extracted copolymers have useful properties. The obtained data are promising in the perspective of developing a microbial PHAs production as a part of an integrated valorization process of high CAs content waste-derived streams.

Phytochemical Screening and Characterization of Agarwood (Aquilaria malaccensis) Chips Wood Grade as Incense Headspace Volatile Compounds by GC-MS.Ms.Q.TOF, SPME

AbstractAgarwood (Aquilaria malaccensis) is an Asian tree traditionally used for many medicinal purposes, its oil constituents and inhaled vapor has sedative, antidepressant and anxiolytic activities. Gas Chromatography and quadruple time of flight –mass spectrometry (GC.MS.MS/Q.TOF) in the MS-MS mode has been used in screening and identification of multiple compounds of three different grade of agarwood chipwood, using DB-1 column which led to identification of 96 compounds while the majority of the compounds about 500 compounds remain UN knowing to the difficulties of confirming or rejecting them . The generated results were so complicated and very difficult to be interpreted for the presence of isomers with similar matched spectrums; the absence of official standard references for these compounds make the judgment of confirming the identified compounds more complicated and very hard to absolute identification to be assessed. The compounds were extracted by applying a solvent less technique; trapping incense and volatile headspace. The total Ion chromatogram detected compounds are distributed among different array over the chemical families among monoterpenes, sesquiterpenes, hydrocarbons, oxygenated monoterpenes, sesquiterpenes, norterpenoids and diterpenoids ,short chain glycols, carboxylic acids and others. The flowing compounds are the major terpene, sesquiterpene and oxygenated sesquiterpenoid found in all grades of A. malaccensis chipswood under investigation, furthermore; the study represented that the characterization of compounds from agarwood chips wood is highly possible through incense volatile sample.

Waste-Derived Fuels and Renewable Chemicals for Bioeconomy Promotion: A Sustainable Approach.

Bio-based fuels and chemicals through the biorefinery approach has gained significant interest as an alternative platform for the petroleum-derived processes as these biobased processes are noticed to have positive environmental and societal impacts. Decades of research was involved in understanding the diversity of microorganisms in different habitats that could synthesize various secondary metabolites that have functional potential as fuels, chemicals, nutraceuticals, food ingredients, and many more. Later, due to the substrate-related process economics, the diverse low-value, high-carbon feedstocks like lignocellulosic biomass, industrial byproducts, and waste streams were investigated to have greater potential. Among them, municipal solid wastes can be used as the source of substrates for the production of commercially viable gaseous and liquid fuels, as well as short-chain fattyacids and carboxylic acids. In this work, technologies and processes demanding the production of value-added products were explained in detail to understand and inculcate the value of municipal solid wastes and the economy, and it can provide to the biorefinery aspect.

Environment-Friendly Catalytic Mineralization of Phenol and Chlorophenols with Cu- and Fe- Tetrakis(4-aminophenyl)-porphyrin—Silica Hybrid Aerogels

Fenton reactions with metal complexes of substituted porphyrins and hydrogen peroxide are useful tools for the mineralization of environmentally dangerous substances. In the homogeneous phase, autooxidation of the prophyrin ring may also occur. Covalent binding of porphyrins to a solid support may increase the lifetime of the catalysts and might change its activity. In this study, highly water-insoluble copper and iron complexes of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin were synthesized and bonded covalently to a very hydrophilic silica aerogel matrix prepared by co-gelation of the propyl triethoxysilyl-functionalized porphyrin complex precursors with tetramethoxysilane, followed by a supercritical carbon dioxide drying. In contrast to the insoluble nature of the porphyrin complexes, the as-prepared aerogel catalysts were highly compatible with the aqueous phase. Their catalytic activities were tested in the mineralization reaction of phenol, 3-chlorophenol, and 2,4-dichlorophenol with hydrogen peroxide. The results show that both aerogels catalyzed the oxidation of phenol and chlorophenols to harmless short-chained carboxylic acids under neutral conditions. In batch experiments, and also in a miniature continuous-flow tubular reactor, the aerogel catalysts gradually reduced their activity, due to the slow oxidation of the porphyrin ring. However, the rate and extent of the degradation was moderate and did not exclude the possibility that the as-prepared catalysts, as well as their more stable derivatives, might find practical applications in environment protection.

Transporter-Driven Engineering of a Genetic Biosensor for the Detection and Production of Short-Branched Chain Fatty Acids in Saccharomyces cerevisiae.

Biosensors can be used for real-time monitoring of metabolites and high-throughput screening of producer strains. Use of biosensors has facilitated strain engineering to efficiently produce value-added compounds. Following our recent work on the production of short branched-chain fatty acids (SBCFAs) in engineered Saccharomyces cerevisiae, here we harnessed a weak organic acid transporter Pdr12p, engineered a whole-cell biosensor to detect exogenous and intracellular SBCFAs and optimized the biosensor’s performance by varying PDR12 expression. We firstly constructed the biosensor and evaluated its response to a range of short-chain carboxylic acids. Next, we optimized its sensitivity and operational range by deletion and overexpression of PDR12. We found that the biosensor responded to exogenous SBCFAs including isovaleric acid, isobutyric acid and 2-methylbutanoic acid. PDR12 deletion enhanced the biosensor’s sensitivity to isovaleric acid at a low concentration and PDR12 overexpression shifted the operational range towards a higher concentration. Lastly, the deletion of PDR12 improved the biosensor’s sensitivity to the SBCFAs produced in our previously engineered SBCFA-overproducing strain. To our knowledge, our work represents the first study on employing an ATP-binding-cassette transporter to engineer a transcription-factor-based genetic biosensor for sensing SBCFAs in S. cerevisiae. Our findings provide useful insights into SBCFA detection by a genetic biosensor that will facilitate the screening of SBCFA-overproducing strains.

Mathematical model of a microbial electrosynthesis cell for the conversion of carbon dioxide into methane and acetate

CO2 conversion to methane and short-chain carboxylic acids in a microbial electrosynthesis cell (MESC) is an emerging approach for combining CO2 sequestration with the production of valuable commodities from a renewable source of carbon. While the production of CH4 and carboxylic acids, such as acetate, was demonstrated in several studies, process scale-up requires a simulation tool for a thorough system analysis, optimization, and a techno-economic assessment. The dynamic mathematical model developed in this work simulates the production of H2 via electrochemical and bio-electrochemical pathways and the formation of CH4 and acetate from CO2 at the MESC cathode taking into account the non-linear dynamics of microbial growth and CO2 conversion, the effects of various operating conditions, and CO2 transport between the MESC electrode compartments. Furthermore, the model simulates the growth of the three key biomass populations of acetogenic, methanogenic and electroactive microorganisms. Parameter identification followed by model validation demonstrated a reasonable agreement between the model predictions and the experimental results. The model was used to predict changes in CH4 and acetate production in response to changing MESC operating conditions.

Metabolic Alteration of Trypanosoma cruzi during Differentiation of Epimastigote to Trypomastigote Forms.

Intracellular parasites such as Trypanosoma cruzi need to acquire valuable carbon sources from the host cell to replicate. Here, we investigated the energetic metabolism of T. cruzi during metacyclogenesis through the determination of enzymatic activities and quantification by HPLC of glycolytic and Krebs cycle short-chain carboxylic acids. Altered concentrations in pyruvate, acetate, succinate, and glycerate were measured during the growth of epimastigote in the complex medium BHI and their differentiation to trypomastigotes in the chemically defined medium, TAU3AAG. These alterations should represent significant differential metabolic modifications utilized by either form to generate energy. This paper is the first work dealing with the intracellular organic acid concentration measurement in T. cruzi parasites. Although it confirms the previous assumption of the importance of carbohydrate metabolism, it yields an essential improvement in T. cruzi metabolism knowledge.

The influence of different carbon sources on growth and single cell oil production in oleaginous yeasts Apiotrichum brassicae and Pichia kudriavzevii

Oleaginous yeasts offer an interesting possibility for renewable lipid production, since the single cell oil accumulated can be based on a wide range of cheap, waste-derived carbon sources. Here, several short chain carboxylic acids and sugars commonly found in these substrates were assessed as carbon sources for Apiotrichum brassicae and Pichia kudriavzevii. While both strains were able to utilize all carbon sources employed, high volumetric lipid productivities (0.4 g/Lh) and lipid contents (68%) could be reached particularly with acetic acid as carbon source. Odd-numbered volatile fatty acids led to lower productivities and lipid contents, but the lipids contained unusually high proportions of odd-numbered fatty acids (up to 80% of total fatty acids). These fatty acids are rather uncommon in nature and might offer the possibility for various high value applications. In conclusion both strains are able to utilize a wide range of substrates potentially present in waste-derived substrates. Lipid content and volumetric lipid productivity strongly depend on the carbon source, with even-numbered volatile fatty acids resulting in the highest values. For volatile fatty acids in particular, the carbon source also strongly influences the composition of the lipids produced by the yeast strains.

P718 Characterization of microbiota and metabolomic profile in human colonic surgical resections of UC patients

Abstract Background Ulcerative colitis (UC) is characterized by a diffuse, continuous, and chronic inflammation of mucosa and submucosa layers in the colon whose etiology is still unknown. Intestinal microbiota dysbiosis and alterations in the metabolomic profile have been reported in mucosal biopsies from Inflammatory Bowel Disease (IBD) patients. We aim to characterize the microbiota composition and metabolomic profile in colonic resections of UC patients. Methods Colonic resections from UC (n=18) and non-IBD (n=20) patients were obtained. Microbiota identification, composition and classification was performed by 16S rRNA gene Illumina Miseq sequencing. The bioinformatic analysis of sequencing data was performed using constrained correspondence analysis (CCA) and non-parametric Wilcoxon test to compare species and genera proportions. Bacterial load was estimated by qPCR. Metabolomic analysis was performed using Nuclear Magnetic Resonance (NMR) to study polar metabolites and Gas-Chromatography or Liquid-Chromatography Mass-Spectrometry to study non-polar metabolites. Results Microbiota analysis revealed differences at genus and species level between UC and non-IBD patients. Cellulosimicrobium was found at 10-fold higher levels in UC samples while Escherichia genus was 3.88 times more abundant in controls. A reduction in bacterial load was seen in UC samples. Levels of short-chain fatty acids (FA), medium-chain FA, long-chain FA, carboxylic acids and amino acids were obtained from the metabolomics analysis and a positive correlation between propionic, aspartic and hydroxybutyric acids and Cellulosimicrobium and Pseudomonas was found (Fig1B). Gut commensals such as unclassified Agathobacter, Blautia faecis, Oscillospiraceae or Faecalibacterium prausnitzii positively correlated with the abundance of butyric acid, acetic acid and succinic acid; meanwhile Subdoligranulum, Lachnospireace or unclassified Blautia negatively correlated with some medium or long chain fatty acids (Fig1B). Fig1. Correlations between bacterial species and metabolites in (A) controls and (B) UC patients. Performed with mixOmics library in R. Conclusion Significant differences in microbiota composition and abundance are found in UC patients, which undergo a clear gut dysbiosis in colonic tissue. Correlation analysis suggests Cellulosimicrobium and Pseudomonas as sources of propionic, aspartic and hydroxybutyric acid. These results point at Cellulosimicrobium as a potential candidate in UC pathology.

Solar photocatalytic degradation of parabens using UiO-66-NH2

The photocatalytic degradation of methylparaben was investigated under simulated solar light using a synthesised metal–organic framework (UiO-66-NH2). For that purpose, the pollutant was spiked in different water matrices: distilled water, water from Lima River (Northwestern Portugal), and urban wastewater. Complete removal of the methylparaben in distilled water was achieved in 1 h reaction. In natural water matrices, the photocatalytic performance decreased to 70% removal after 3 h reaction, owing to the physical–chemical properties of the water samples. The UiO-66-NH2 photocatalyst revealed high stability under the continuous mode, reaching a steady state in 5 h, from which the removal percentage was kept constant for 25 h. The photocatalytic degradation of methylparaben gave five main reaction byproducts and four short-chain carboxylic acids, identified by LC/ESI-MS and UHPLC analyses, respectively. The mechanism of degradation was investigated by using selective scavengers. Photogenerated holes and superoxide radicals were found as the main species responsible for the degradation of methylparaben. The abatement of other parabens (as ethyl- and propylparaben) was also evaluated, being the conversion influenced by the length of the alkyl side chain. The results of this study give a comprehensive sight into the effective photocatalytic remediation of parabens using UiO-66-NH2.

Effect of concentrated NaCl on catalytic wet oxidation (CWO) of short chain carboxylic acids

The effect of concentrated NaCl (200 g L−1) on CWO of oxalic acid and acetic acid over MnCeOx was investigated at 110 °C and 0.5 MPa O2 to explore the potential of using CWO for shale gas wastewater treatment. The presence of concentrated NaCl hindered oxalic acid conversion, which from ATR-IR spectroscopy was attributed to the salting out effect increasing the oxalic acid surface coverage with formation of strongly adsorbed intermediates, slowing oxalic acid mineralisation. In addition, the weak adsorption of acetic acid on MnCeOx was proposed to be responsible for the insignificant conversion with or without NaCl present.

Co-occurrence and correlations of PFASs and chlorinated volatile organic compounds (cVOCs) in subsurface in a fluorochemical industrial park: Laboratory and field investigations

Fluorochemical industrial park (FIP) represents an important source of per- and polyfluoroalkyl substances (PFASs) and chlorinated volatile organic compounds (cVOCs). Exploring the co-occurrence and correlations of PFASs and cVOCs is a key step towards the understanding their distributions in the field. In this study, perfluorooctanoic acid (PFOA) was the dominant compound in groundwater and aquifer solids, and elevated concentrations of short-chain perfluoroalkyl carboxylic acids (PFCAs) and hexafluoropropylene oxide oligomers were also detected in the field, suggesting their wide applications as substitutes for PFOA. Correlation analyses between PFASs and cVOCs suggested that cVOCs had a significant influence on the distribution and composition of PFASs in the field. In addition, the presence of cVOCs in the form of dense non-aqueous-phase organic liquids (DNAPL) affected the distribution and migration of PFASs at various depths, as evidenced by the relatively high PFASs concentrations (204 μg/L) and PFOA abundance (85.4%) in the deep aquifer, likely due to DNAPL-water interfaces sorption or partition into bulk DNAPL. The log Kd values, determined in the laboratory, were found to increase in the presence of DNAPL, especially for PFOA, with more than one time higher than those of perfluorobutanoic acid (PFBA) and hexafluoropropylene oxide dimer acid (HFPO-DA). This conclusion further demonstrated that PFOA had a higher potential to participate into DNAPL, which can migrate with DNAPL to the deep aquifer, supporting the higher abundance of PFOA in the deep aquifer mentioned above. However, the log Kd-field values of PFBA and HFPO-DA in the field were higher than that of PFOA, and no significant correlations (p > 0.05) were found between log Kd-field values and the chain-length of PFCAs at various depths, suggesting that the phenomena observed in the field are a result of composite influencing factors.

Distributions and sources of traditional and emerging per- and polyfluoroalkyl substances among multiple environmental media in the Qiantang River watershed, China.

The presence of per- and polyfluoroalkyl substances (PFASs) in the food chain poses a threat to human health. Water and the atmosphere are the major transport pathways for PFASs in the environment, while water, soil and sediment are sinks. Herein, the concentrations and distributions of traditional and emerging PFASs in multi-environmental media samples in the Qiantang River watershed were comprehensively investigated. Twenty-five PFASs, including seven emerging PFASs, were identified. The concentrations in water, soil, sediment and PM2.5 ranged from 3.58 to 786 ng L−1, 0.72 to 12.3 ng g−1, 0.73 to 6.60 ng g−1, and 93.9 to 255 pg m−3, respectively, with mean concentrations of 149 ng L−1, 4.70 ng g−1, 4.31 ng g−1, and 156 pg m−3. Perfluorooctanoic acid (PFOA) was the dominant contaminant in water, soil, and sediment, and perfluoropentanoic acid (PFPeA) was the dominant contaminant in PM2.5. Hexafluoropropylene oxide-dimer acid (HFPO-DA) and 6 : 2 chlorinated polyfluorinated ether sulfonate (6 : 2 Cl-PFESA), as substitutes for PFOA and perfluorooctane sulfonate (PFOS), were detected, indicating the gradual replacement of traditional PFOA and PFOS in this area. Perfluoro-3,6-dioxaheptanoic acid (NFDHA), as a component of the aqueous film-forming foam FN-3, was first detected in this area. Short-chain PFASs were mainly distributed in water and PM2.5, while long-chain PFASs were distributed in the solid phase, such as soil, sediment, and PM2.5. Based on principal component analysis (PCA), the major PFAS sources were emulsifiers from fluorine polymerization and surface-active agents from the textile, papermaking, leather, and other industries. In addition, correlation analysis showed that water was the main source and transport pathway of short-chain perfluoroalkyl carboxylic acid (PFCA), HFPO-DA, and NFDHA in this area, while the atmosphere combined with PM2.5 was the main transport pathway for both short- and long-chain PFCAs, PFOS, and 6 : 2 Cl-PFESA.

Effect of Solution Chemistry on the Transport of Short-Chain and Long-Chain Perfluoroalkyl Carboxylic Acids (Pfcas) in Saturated Porous Media

Effect of Solution Chemistry on the Transport of Short-Chain and Long-Chain Perfluoroalkyl Carboxylic Acids (Pfcas) in Saturated Porous Media

Application of high-throughput transcriptomics for mechanism-based biological read-across of short-chain carboxylic acid analogues of valproic acid.

Chemical read-across is commonly evaluated without specific knowledge of the biological mechanisms leading to observed adverse outcomes in vivo. Integrating data that indicate shared modes of action in humans will strengthen read-across cases. Here we studied transcriptomic responses of primary human hepatocytes (PHH) to a large panel of carboxylic acids to include detailed mode-of-action data as a proof-of-concept for read-across in risk assessment. In rodents, some carboxylic acids, including valproic acid (VPA), are known to cause hepatic steatosis, whereas others do not. We investigated transcriptomics responses of PHHs exposed for 24 h to 18 structurally different VPA analogues in a concentration range to determine biological similarity in relation to in vivo steatotic potential. Using a targeted high-throughput screening assay, we assessed the differential expression of ~3,000 genes covering relevant biological pathways. Differentially expressed gene analysis revealed differences in potency of carboxylic acids, and expression patterns were highly similar for structurally similar compounds. Strong clustering occurred for steatosis-positive versus steatosis-negative carboxylic acids. To quantitatively define biological read-across, we combined pathway analysis and weighted gene co-expression network analysis. Active carboxylic acids displayed high similarity in gene network modulation. Importantly, free fatty acid synthesis modulation and stress pathway responses are affected by active car­boxylic acids, providing coherent mechanistic underpinning for our findings. Our work shows that transcriptomic analysis of cultured human hepatocytes can reinforce the prediction of liver injury outcome based on quantitative and mechanistic biological data and support its application in read-across.