A year-round observation of δ13C of dicarboxylic acids and related compounds in fine aerosols: Implications from Central European background site.

Isotopic analysis of specific compounds in aerosols can be a useful tool when studying atmospheric processes. Here, we present the results of stable carbon isotope ratio (δ13C) measurements performed on a one-year set (n = 96, Sep. 2013-Aug. 2014) of dicarboxylic acids and related compounds in PM1 at a rural Central European background site, Kosetice (Czech Republic). The most 13C enriched acid was oxalic (C2, annual average = -16.6 ± 5.0‰) followed by malonic (C3, avg. = -19.9 ± 6.6‰) and succinic (C4, avg. = -21.3 ± 4.6‰) acids. Thus, δ13C values decreased with an increase in carbon numbers. Azelaic acid (C9, avg. = -27.2 ± 3.6‰) was found to be the least 13C enriched. A comparison of δ13C of dicarboxylic acids from other background sites, especially in Asia, shows similar values to those from the European site. This comparison also showed that C2 is more 13C enriched at background sites than at urban ones. In general, we did not observe significant seasonal differences in δ13C values of dicarboxylic acids at the Central European station. We observed statistically significant differences (p value < 0.05) between winter and summer δ13C values solely for C4, glyoxylic acid (ωC2), glutaric acid (C5) and suberic acid (C8). The only significant correlations between δ13C of C2 and δ13C of C3 were found in spring and summer, suggesting that the oxidation of C3 to C2 is significant in these months with a strong contribution from biogenic aerosols. The strongest season-independent annual correlation was observed in δ13C values between C2 and C4, the two dominant dicarboxylic acids. Therefore, C4 appears to be the main intermediate precursor of C2 throughout the whole year.

PM2.5 chemical composition and health risks by inhalation near a chemical complex.

Particulate matter (PM2.5) samples were collected in the vicinity of an industrial chemical pole and analysed for organic and elemental carbon (OC and EC), 47 trace elements and around 150 organic constituents. On average, OC and EC accounted for 25.2% and 11.4% of the PM2.5 mass, respectively. Organic compounds comprised polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs, anhydrosugars, phenolics, aromatic ketones, glycerol derivatives, aliphatic alcohols, sterols, and carboxyl groups, including aromatic, carboxylic and dicarboxylic acids. Enrichment factors > 100 were obtained for Pb, Cd, Zn, Cu, Sn, B, Se, Bi, Sb and Mo, showing the contribution of industrial emissions and nearby major roads. Principal component analysis revealed that vehicle, industrial and biomass burning emissions accounted for 66%, 11% and 9%, respectively, of the total PM2.5-bound PAHs. Some of the detected organic constituents are likely associated with plasticiser ingredients and thermal stabilisers used in the manufacture of PVC and other plastics in the industrial complex. Photooxidation products of both anthropogenic (e.g., toluene) and biogenic (e.g., isoprene and pinenes) precursors were also observed. It was estimated that biomass burning accounted for 13.8% of the PM2.5 concentrations and that secondary OC represented 37.6% of the total OC. The lifetime cancer risk from inhalation exposure to PM2.5-bound PAHs was found to be negligible, but it exceeded the threshold of 10-6 for metal(loi)s, mainly due to Cr and As.

Molecular characterization and spatial distribution of dicarboxylic acids and related compounds in fresh snow in China.

Low molecular weight organic compounds are ubiquitous in the atmosphere. However, knowledge on their concentrations and molecular distribution in fresh snow remains limited. Here, twelve fresh snow samples collected at eight sites in China were investigated for dicarboxylic acids and related compounds (DCRCs) including oxocarboxylic acids and α-dicarbonyls. Dissolved organic carbon (DOC) concentrations in the snow samples ranged from 0.99 to 14.6 mg C L-1. Concentrations of total dicarboxylic acids were from 225 to 1970 µg L-1 (av. 650 µg L-1), while oxoacids (28.3-173, av. 68.1 µg L-1) and dicarbonyls (12.6-69.2, av. 31.3 µg L-1) were less abundant, accounting for 4.6-8.5% (6.2%), 0.45-1.4% (0.73%), and 0.12-0.88% (0.46%) of DOC, respectively. Molecular patterns of dicarboxylic acids are characterized by a predominance of oxalic acid (C2) (95.0-1030, av. 310 µg L-1), followed by phthalic (Ph) (9.69-244, av. 69.9 µg L-1) or succinic (C4) (23.8-163, av. 63.7 µg L-1) acid. Higher concentrations of Ph in snow from Beijing and Tianjin than other urban and rural regions suggest significant emissions from vehicular exhausts and other fossil fuel combustion sources in megacities. C2 constituted 40-54% of total diacids, corresponding to 1.5-2.6% of snow DOC. The total measured DCRCs represent 5.5-10% of snow DOC, which suggests that there are large amounts of unknown organics requiring further investigations. The spatial distributions of diacids exhibited higher loadings in megacities than rural and island sites. Molecular distributions of diacids indicated that the photochemical modification was restrained under the weak solar radiation during the snow events, while anthropogenic primary sources had a more significant influence in megacities than rural areas and islands.

Characterization of dicarboxylic acids, oxoacids, and α-dicarbonyls in PM2.5 within the urban boundary layer in southern China: Sources and formation pathways.

Low-molecular-weight dicarboxylic acids, which are important components of secondary organic aerosols, have been extensively studied in recent years. Many studies have focused on ground-level observations and literature reports on the vertical distribution of the organic aerosols within the urban boundary layer are limited. In this study, the vertical profiles of dicarboxylic acids and related organic compounds (DCRCs) in PM2.5 were investigated at altitudinal levels (ground level and 488 m above the ground level) at the Canton Tower in Guangzhou, southern China, to elucidate their primary sources and secondary formation processes. The concentrations of DCRCs at ground level were generally higher than those at 488 m. Oxalic acid (C2) was the most abundant species, followed by succinic acid (C4) and malonic acid (C3) at both heights. The higher ratio of DCRCs-bound carbon to organic carbon (i.e., DCRCs-C/OC) at 488 m (4.8 ± 1.2%) relative to that at ground level (2.7 ± 0.5%) indicated a higher degree of aerosol aging at 488 m. The abundance of C2 was increased and the conversion of C4 to C3 was enhanced due to the photochemical oxidation of its homologues during long-range transport periods. The increase in C2 was associated with in-cloud processes during pollution periods. Principal component analysis showed that DCRCs were mainly derived from atmospheric secondary processing and biomass burning was also an important source of long-chain carboxylic acids during autumn in Guangzhou. Our results illustrate that secondary processing and biomass burning play prominent roles in controlling the abundance of DCRCs. Furthermore, DCRCs are affected by air masses from regional areas, oxidation of their precursors via vertical transport and in-cloud processes.

Vortex assisted liquid-liquid microextraction based on in situ formation of a natural deep eutectic solvent by microwave irradiation for the determination of beta-blockers in water samples.

In this study, a simple, green, and reliable method combining vortex-assisted liquid-liquid microextraction based on in situ formation of a novel hydrophobic natural deep eutectic solvent (NADES-VA-LLME) and high-performance liquid chromatography (HPLC) was developed for the determination of metoprolol and propranolol in water samples. The novel NADES was synthesized in situ within only 20 s by subjecting the water sample containing azelaic acid and thymol to microwave irradiation at 50 ˚C. Initial studies indicated that a 17:1 ratio of thymol to azelaic acid yielded the highest response for analytes. The influence of 7 parameters, including NADES volume, salt amount, sample pH, vortex time, centrifugation time, microwave time, and temperature, were screened using a 27-3 fractional factorial design. The obtained significant parameters were optimized by response surface methodology employing a Box-Behnken design. The method displayed satisfactory linearity (r=0.9996) for metoprolol and propranolol with limits of detection of 0.2 and 0.1 µg/L, respectively. The relative standard deviation at 2.5, 40, and 80 µg/L levels was lower than 6%, with accuracy in the range of 90.8-100.2%. Enrichment factors were 147.0 and 144.4 for metoprolol and propranolol, respectively. This study demonstrates that the developed in situ NADES-VA-LLME-HPLC technique can be considered as a fast and environmentally friendly alternative for isolation/preconcentration of ß-blockers from water samples.

trans-3-Methylglutaconyl CoA isomerization-dependent protein acylation.

3-methylglutaconic (3MGC) aciduria is associated with a growing number of discrete inborn errors of metabolism. Herein, an antibody-based approach to detection/quantitation of 3MGC acid has been pursued. When trans-3MGC acid conjugated keyhole limpet hemocyanin (KLH) was inoculated into rabbits a strong immune response was elicited. Western blot analysis provided evidence that immune serum, but not pre-immune serum, recognized 3MGC-conjugated bovine serum albumin (BSA). In competition ELISAs using isolated immune IgG, the limit of detection for free trans-3MGC acid was compared to that for cis-3MGC acid and four structurally related short-chain dicarboxylic acids. Surprisingly, cis-3MGC acid yielded a much lower limit of detection (∼0.1 mg/ml) than trans-3MGC acid (∼1.0 mg/ml) while all other dicarboxylic acids tested were poor competitors. The data suggest trans-3MGC- isomerized during, or after, conjugation to KLH such that the immunogen was actually comprised of KLH harboring a mixture of cis- and trans-3MGC haptens. To investigate this unexpected isomerization reaction, trans-3MGC CoA was prepared and incubated at 37 °C in the presence of BSA. Evidence was obtained that non-enzymatic isomerization of trans-3MGC CoA to cis-3MGC CoA precedes intramolecular catalysis to form cis-3MGC anhydride plus CoASH. Anhydride-dependent acylation of BSA generated 3MGCylated BSA, as detected by anti-3MGC immunoblot. The results presented provide an explanation for the unanticipated detection of 3MGCylated proteins in a murine model of primary 3MGC aciduria. Furthermore, non-enzymatic hydrolysis of cis-3MGC anhydride represents a potential source of cis-3MGC acid found in urine of subjects with 3MGC aciduria.

Biomarkers for the toxicity of sublethal concentrations of triclosan to the early life stages of carps.

Accumulation, contents of protein, non-enzymatic antioxidant glutathione (GSH and GSSG), lipid peroxidation product (melondialdehyde-MDA) and organic acids (fumarate, succinate, malate and citrate), and activities of neurological (acetylcholinesterase-AChE), detoxification (glutathione S-transferase-GST) and metabolic (lactate dehydrogenase-LDH, aspartate transaminase-AST and alanine transaminase-ALT) enzymes were recorded in the hatchlings of Cyprinus carpio, Ctenopharyngodon idella, Labeo rohita and Cirrhinus mrigala after 7 and 14 days exposure and 10 days post exposure (recovery period) to sublethal concentrations (0.005, 0.01, 0.02 and 0.05 mg/L) of triclosan, a highly toxic and persistent biocide used in personal care products. Accumulation was maximum between 7-14 days at 0.01 mg/L for C. carpio and L. rohita but at 0.005 mg/L for C. idella and C. mrigala. No triclosan was observed at 0.005 mg/L in C. carpio and C. mrigala after recovery. Significant decline in protein, glutathione and acetylcholinesterase but increase in glutathione S-transferase, lactate dehydrogenase, aspartate transaminase, alanine transaminase, melondialdehyde and organic acids over control during exposure continued till the end of recovery period. Integrated biomarker response (IBR) analysis depicted higher star plot area for glutathione and glutathione S-transferase during initial 7 days of exposure, thereafter, during 7-14 days of exposure and the recovery period, higher star plot area was observed for acetylcholinesterase, aspartate transaminase, alanine transaminase and organic acids. Higher star plot area was observed for protein in all the species throughout the study. The study shows that L. rohita is most sensitive and glutathione, acetylcholinesterase, aspartate transaminase and alanine transaminase are the biomarkers for the toxicity of sublethal concentrations of TCS.

Engineering Stable Pseudomonas putida S12 by CRISPR for 2,5-Furandicarboxylic Acid (FDCA) Production.

FDCA (2,5-furandicarboxylic acid) can be enzymatically converted from HMF (5-hydroxymethylfurfural). Pseudomonas putida S12 is promising for FDCA production, but generating stable P. putida S12 is difficult due to its polyploidy and lack of genome engineering tools. Here we showed that coupling CRISPR and λ-Red recombineering enabled one-step gene integration with high efficiency and frequency, and simultaneously replaced endogenous genes in all chromosomes. Using this approach, we generated two stable P. putida S12 strains expressing HMF/furfural oxidoreductase (HMFH) and HMF oxidase (HMFO), both being able to convert 50 mM HMF to ≈42-43 mM FDCA in 24 h. Cosupplementation of MnO2 and CaCO3 to the medium drastically improved the cell tolerance to HMF and enhanced FDCA production. Cointegrating HMFH and HMFT1 (HMF transporter) genes further improved FDCA production, enabling the cells to convert 250 mM HMF to 196 mM (30.6 g/L) FDCA in 24 h. This study implicates the potentials of CRISPR for generating stable P. putida S12 strains for FDCA production.

Hedychium coronarium Rhizomes: Promising Antidiabetic and Natural Inhibitor of α-Amylase and α-Glucosidase.

Hedychium coronarium Koen., commonly known as ginger lily, is considered an endemic medicinal plant. In the present study, the antidiabetic action of its rhizomes was investigated by α-amylase and α-glucosidase inhibition assay, and the active compounds were identified through bioactivity guided isolation technique. Among the six different extracts, the EA extract has shown highest inhibition, and the subfractions from active EA extract were separated by silica gel column chromatography. The subfraction showing highest inhibition was investigated for its chemical composition by high-resolution liquid chromatography-mass spectroscopy (HRLC-MS/MS). The fatty acids such as suberic acid and terpenes such as triparanol, ginkgolide C, and swietenine were found to be the major compounds in the subfractions. The present work revealed that H. coronarium rhizome extract and its active constituent could be used as a natural inhibitor of these two carbohydrate-metabolizing enzymes and may play a key role in the management of diabetes.

Production of long-chain hydroxy fatty acids by Starmerella bombicola.

To decrease our dependency for the diminishing source of fossils resources, bio-based alternatives are being explored for the synthesis of commodity and high-value molecules. One example in this ecological initiative is the microbial production of the biosurfactant sophorolipids by the yeast Starmerella bombicola. Sophorolipids are surface-active molecules mainly used as household and laundry detergents. Because S. bombicola is able to produce high titers of sophorolipids, the yeast is also used to increase the portfolio of lipophilic compounds through strain engineering. Here, the one-step microbial production of hydroxy fatty acids by S. bombicola was accomplished by the selective blockage of three catabolic pathways through metabolic engineering. Successful production of 17.39 g/l (ω-1) linked hydroxy fatty acids was obtained by the successive blockage of the sophorolipid biosynthesis, the ß-oxidation and the ω-oxidation pathways. Minor contamination of dicarboxylic acids and fatty aldehydes were successfully removed using flash chromatography. This way, S. bombicola was further expanded into a flexible production platform of economical relevant compounds in the chemical, food and cosmetic industries.

Microfluidic device for the point of need detection of a pathogen infection biomarker in grapes.

Bacterial, fungal and viral infections in plant systems are on the rise, most of which tend to spread quickly amongst crops. These pathogens are also gaining resistance to known treatments, which makes their early detection a priority to avoid extensive loss of crops and the spreading of disease to animal systems. In this work, we propose a microfluidic platform coupled with integrated thin-film silicon photosensors for the detection of pathogen infections in grapes. This detection was achieved by monitoring the concentration of Azelaic Acid (AzA). This small organic acid plays a significant role in the defense mechanism in plant systems. In this platform, the enzyme tyrosinase was immobilized on microbeads inside a microfluidic system. By colorimetric monitoring of the inhibitory effect of AzA on the enzyme tyrosinase in real time, it was possible, in under 10 minutes, to detect different concentrations of AzA in both buffer and spiked solutions of grape juice, in both cases with limits of detection in the 5-10 nM range. In addition, with this microfluidic device, it was possible to clearly distinguish infected from healthy grape samples at three different grape maturation points. Healthy grape samples showed AzA concentrations in the range of 10-20 nM (post-dilution) while infected samples have an estimated increase of AzA of 10-30×, results which were confirmed using HPLC. In both juice and grape samples an integrated sample preparation stage that decreases the phenol content of the solutions was required to achieve fit-for-purpose sensitivities to AzA.

A tiered analytical approach for target, non-target and suspect screening analysis of polar transformation products of polycyclic aromatic compounds.

Polycyclic aromatic compounds (PACs) possess toxicity towards humans, and their presence in the environment is unwanted. Polar transformation products (TPs) are more mobile, and can be considered emerging contaminants, as they represent a more bioavailable carrier of the same toxic properties. Acidic TPs has been proposed as an important class of polar TPs. This study presents a tiered analytical approach to investigate acidic and polar PAC TPs in environmental conditions. The tiered approach exploits target analysis for quantification of acids; suspect screening for tentative identification based on retention time and spectral matching using databases; and finally non-target analysis based on chromatography and data independent broadband MS to highlight potentially unknown analyte peaks. The approach includes a mixed-mode anion exchange solid phase extraction (MAX-SPE) to fractionate neutral and acidic compounds, and is applied to three cases: I) Photo-oxidation of six PACs generated suspected hydroxylated-, carbonylated- and carboxylated PACs but also proposed the presence of mono- and dicarboxylic acids, which have not been reported elsewhere. For a subset of four acids, conversion rates were determined. II) Recovery of spiked acids from diesel spilled harbor water was 80% by LC-MS, and diesel spill weathering was evaluated from the neutral fraction by GC-MS. III) By non-target analysis sulfonated PACs, presumable derived from photo-oxidation, were detected in run-off basins of an arctic landfarm, alongside hypothesized naturally occuring fatty acids. The tiered approach is a sensitive and versatile tool to extract information on PACs and their polar TPs from polluted environmental sites.

Dicarboxylic acids and related compounds in fine particulate matter aerosols in Huangshi, central China.

PM2.5 (particulate matter with an aerodynamic diameter <2.5 µm) samples were collected in Huangshi, central China, from March 2012 to February 2013 and were analyzed for dicarboxylic acids (diacids) and related compounds (DARCs). Oxalic acid (C2; 416 ng m-3) was the most abundant species, followed by phthalic (Ph; 122 ng m-3), terephthalic (tPh; 116 ng m-3), succinic (C4; 70.4 ng m-3), azelaic (C9; 67.9 ng m-3), and adipic (C6; 57.8 ng m-3) acids. Relatively high abundances of Ph and tPh differed from the distribution in urban and marine aerosols, indicating contributions from nearby anthropogenic sources. Glyoxylic acid (ωC2; 41.4 ng m-3) was the dominant oxoacid, followed by 9-oxononanoic (ωC9; 40.8 ng m-3) and pyruvic (Pyr; 24.1 ng m-3) acids. Glyoxal (Gly; 35.5 ng m-3) was the dominant α-dicarbonyl. Highest average concentrations were found for C2, ωC2, and C9 in autumn, for C4, for Pyr and C6 in spring, for Ph, ωC9, and Gly in summer, whereas the lowest values were observed in winter. Seasonal variations and correlation coefficients of DARCs demonstrate that both primary emissions and secondary production are important sources. Principal component analysis of selected DARCs species suggests that a mixing of air masses from anthropogenic and biogenic sources contribute to the Huangshi aerosols. Implications: Both primary emissions and secondary production are important sources of diacids and related compounds in PM2.5 from Huangshi, central China. Principal component analysis of selected diacids in Huangshi aerosols suggests that mixing of air masses from anthropogenic and biogenic sources contribute to ambient aerosols in central China.

The spent culture supernatant of Pseudomonas syringae contains azelaic acid.

BACKGROUND: Pseudomonas syringae pv. actinidiae (PSA) is an emerging kiwifruit bacterial pathogen which since 2008 has caused considerable losses. No quorum sensing (QS) signaling molecule has yet been reported from PSA and the aim of this study was to identify possible intercellular signals produced by PSA. RESULTS: A secreted metabolome analysis resulted in the identification of 83 putative compounds, one of them was the nine carbon saturated dicarboxylic acid called azelaic acid. Azelaic acid, which is a nine-carbon (C9) saturated dicarboxylic acid, has been reported in plants as a mobile signal that primes systemic defenses. In addition, its structure,(which is associated with fatty acid biosynthesis) is similar to other known bacterial QS signals like the Diffusible Signal Facor (DSF). For these reason it could be acting as s signal molecule. Analytical and structural studies by NMR spectroscopy confirmed that in PSA spent supernatants azelaic acid was present. Quantification studies further revealed that 20 µg/L of were present and was also found in the spent supernatants of several other P. syringae pathovars. The RNAseq transcriptome study however did not determine whether azelaic acid could behave as a QS molecule. CONCLUSIONS: This study reports of the possible natural biosynthesis of azelaic acid by bacteria. The production of azelaic acid by P. syringae pathovars can be associated with plant-bacteria signaling.

Universal response quantification approach using a Corona Charged Aerosol Detector (CAD) - Application on linear and cyclic oligomers extractable from polycondensate plastics polyesters, polyamides and polyarylsulfones.

In terms of risk assessment especially for known and unknown substances migrating from food contact materials, quantification without corresponding reference substances currently poses a challenge. In the present study, the opportunity of a universal response quantification approach was evaluated by using a corona charged aerosol detector (CAD) for liquid chromatography combined with inverse gradient compensation. Characteristics of CAD detection in dependence of substance properties were analyzed with 46 randomly chosen reference substances. An almost equal CAD response (±20%) was achieved for non-volatile substances with a molecular weight of minimum 400 g/mol and a vapor pressure of maximum 10-8 Torr. We empirically defined an analytical parameter, Q50/35, the quotient of CAD peak areas at CAD evaporator temperatures of 50 °C and 35 °C, to predict the adequacy of the CAD universal response approach for quantification of known and unknown analyte substances. Exemplarily, we applied the CAD universal quantification approach for the determination of extractable oligomers below 1000 g/mol from a variety of food contact polycondensate plastic materials (e.g. polyesters like polyethylene terephthalate, polybutylene terephthalate, Tritan copolyester, polyamides 6, 6.6 and 6 T/6I and polyarylsulfones polyphenylsulfone and polyethersulfone). Quantitative results for in total 44 oligomers out of 11 materials were compared with established material-specific quantification methods using extracted oligomer mixtures as well as individual oligomers isolated from the mixtures. CAD-based quantification results were generally in accordance to published quantification approaches for polyamide oligomers and oligomers from polyarylsulfones. For oligomers extracted and isolated from polyester materials a slight underestimation was determined by CAD universal response approach. In terms of detection limits and accuracy, the universal CAD approach exhibits no advantages compared to established UV-methods, to date.

Exposure marker discovery of di(isononyl)cyclohexane-1,2-dicarboxylate using two mass spectrometry-based metabolite profiling data processing methods.

Di(isononyl)cyclohexane-1,2-dicarboxylate (DINCH) is a plasticizer used in polyvinyl chloride (PVC) products, such as toys and food packaging. Because the use of DINCH is on the rise, the risk of human exposure to this chemical may likewise increase. Discovering markers for assessing human chemical exposure is difficult because the metabolism of chemicals within humans is complex. In this study, two mass spectrometry (MS)-based metabolite profiling data processing methods, the mass defect filter (MDF) method and the signal mining algorithm with isotope tracing (SMAIT) method, were used for DINCH metabolite discovery, and 110 and 18 potential DINCH metabolite signal candidates were discovered, respectively, from in vitro DINCH incubation samples. Of these, the 21 signals were validated as tentative exposure marker signals in a rat model. Interestingly, the two methods generated rather different sets of DINCH exposure markers. Five of the 21 tentative exposure marker signals were verified as the probable DINCH structure-related metabolite signals based on their MS/MS product ion profiles. These five signals were detected in at least one human urine sample. Of the five probable DINCH structure-related metabolite signals, two novel signals might be suitable exposure markers that should be further investigated for their application in human DINCH exposure assessments. These observations indicate that the MDF and SMAIT methods may be used to discover a relatively different set of potential DINCH exposure markers.

Study of polar organic compounds in airborne particulate matter of a coastal urban city.

Two classes of polar organic compounds, dicarboxylic acids (DCAs) and sugars/sugar anhydrides (S/SAs), were measured in airborne particulate matter in the area of Thessaloniki, northern Greece. The target compounds were measured simultaneously in two particle fractions PM10 and PM2.5 during cold and warm periods by employing extraction in an ultrasonic bath with a mixture of MeOH/DCM (1:2 v/v), derivatization with BSTFA-TMCS and GC-MS for analysis. At both fractions, phthalic was the predominant carboxylic acid during cold season and a-ketoglutaric acid in warm season, followed by maleic and malic. Levoglucosan was the dominant sugar anhydride during the cold and arabitol during the warm season. In total, the distribution of DCAs seemed to favor the PM2.5 particle fraction, probably due to anthropogenic emissions and photochemical formation. The relative contribution of DCAs to PM2.5 fraction was 0.9-3.2% in cold and 0.9-7.0% in warm period. Regarding S/SAs, levoglucosan was also predominantly distributed in fine particles, with relative contribution to this fraction 0.1-6.3% in cold and <0.65% in warm season, suggesting impact of biomass burning emissions. In contrast, arabitol, fructose, and glucose were mainly found in coarse fraction, possibly due to their biogenic origin. Negative correlation of target compounds with temperature and total solar radiation suggested the contribution of seasonal dependant local sources. Positive relationship with NO and NO2 oxidants and relative humidity showed secondary formation of polar compounds or enhanced gas-to-particle conversion.

High-resolution dynamic computer simulation of electrophoresis using a multiphysics software platform.

The modeling and simulation software COMSOL Multiphysics® was recently extended with an electrophoretic transport interface. Its performance was investigated by comparison to results obtained using the 1D dynamic electrophoresis simulators GENTRANS and SIMUL5. Simulations of zone electrophoresis, isotachophoresis, isoelectric focusing and of an oscillating electrolyte system were performed. Smooth profiles were essentially identical indicating that the COMSOL electrophoretic transport interface is able to reproduce results of the 1D simulators. Differences in the way the respective numerical schemes handle steep concentration gradients and associated instabilities were observed. The COMSOL electrophoretic transport interface is expected to be useful as a general model for simulations in 1D, 2D or 3D geometries, as well as for simulations combining electrophoresis with other physical phenomena.

Effects of glucose concentration on 1,18-cis-octadec-9-enedioic acid biotransformation efficiency and lipid body formation in Candida tropicalis.

The unsaturated long-chain α,ω-dicarboxylic acid 1,18-cis-octadec-9-enedioic acid (cis-ODA) is a versatile precursor of various valuable compounds, such as polymers, and can be obtained from renewable resources. This makes cis-ODA highly attractive for the chemical industry where there is a growing interest in sustainable processes. However, chemical synthesis of the cis isomers is currently not feasible. In contrast, biotechnological production allows for highly specific and selective reactions. Therefore, we developed an efficient production strategy for cis-ODA using Candida tropicalis as a whole-cell biocatalyst for the biotransformation of oleic acid, which naturally occurs in various fats and oils. Applying a bench-top system comprising eight parallel bioreactors, the production process was characterised and optimised for high productivity. Glucose feed rate was identified as the most crucial process parameter influencing product yield, with high rates inducing oleic acid incorporation into triacylglycerols and storage in lipid bodies. Conversely, application of medium-chain length fatty acid as a substrate did not show any occurrence of lipid bodies. Applying the lowest possible molar ratio of glucose to oleic acid (1.5) resulted in marginal lipid body formation, but led to a peak volumetric productivity of 0.56 g/L/h and a final titre of approximately 45 g/L with a corresponding yield of 70%.

Chemical characteristics of dicarboxylic acids and related organic compounds in PM2.5 during biomass-burning and non-biomass-burning seasons at a rural site of Northeast China.

Fine particulate matter (PM2.5) samples were collected using a high-volume air sampler and pre-combusted quartz filters during May 2013 to January 2014 at a background rural site (47∘35 N, 133∘31 E) in Sanjiang Plain, Northeast China. A homologous series of dicarboxylic acids (C2-C11) and related compounds (oxoacids, α-dicarbonyls and fatty acids) were analyzed by using a gas chromatography (GC) and GC-MS method employing a dibutyl ester derivatization technique. Intensively open biomass-burning (BB) episodes during the harvest season in fall were characterized by high mass concentrations of PM2.5, dicarboxylic acids and levoglucosan. During the BB period, mass concentrations of dicarboxylic acids and related compounds were increased by up to >20 times with different factors for different organic compounds (i.e., succinic (C4) acid > oxalic (C2) acid > malonic (C3) acid). High concentrations were also found for their possible precursors such as glyoxylic acid (ωC2), 4-oxobutanoic acid, pyruvic acid, glyoxal, and methylglyoxal as well as fatty acids. Levoglucosan showed strong correlations with carbonaceous aerosols (OC, EC, WSOC) and dicarboxylic acids although such good correlations were not observed during non-biomass-burning seasons. Our results clearly demonstrate biomass burning emissions are very important contributors to dicarboxylic acids and related compounds. The selected ratios (e.g., C3/C4, maleic acid/fumaric acid, C2/ωC2, and C2/levoglucosan) were used as tracers for secondary formation of organic aerosols and their aging process. Our results indicate that organic aerosols from biomass burning in this study are fresh without substantial aging or secondary production. The present chemical characteristics of organic compounds in biomass-burning emissions are very important for better understanding the impacts of biomass burning on the atmosphere aerosols.