Long-chain Aliphatic Compounds Research Articles

Generation of long-chain fatty acids by hydrogen-driven bicarbonate reduction in ancient alkaline hydrothermal vents

The origin of life required membrane-bound compartments to allow the separation and concentration of internal biochemistry from the external environment and establish energy-harnessing ion gradients. Long-chain amphiphilic molecules, such as fatty acids, appear strong candidates to have formed the first cell membranes although how they were first generated remains unclear. Here we show that the reaction of dissolved hydrogen and bicarbonate with the iron-rich mineral magnetite under conditions of continuous flow, alkaline pH and relatively low temperatures (90 °C) generate a range of functionalised long-chain aliphatic compounds, including mixed fatty acids up to 18 carbon atoms in length. Readily generated membrane-forming amphiphilic organic molecules in the first cellular life may have been driven by similar chemistry generated from the mixing of bicarbonate-rich water (equilibrated with a carbon dioxide-enriched atmosphere) with alkaline hydrogen-rich fluids fed by the serpentinisation of the Earth’s iron-rich early crust.

Characteristics of polar organic compounds from diesel truck emissions measured by FT-ICR MS

Water-soluble organic compounds (WSOC) and dichloromethane: methanol-soluble organic compounds (DMSOC) in polar organic compounds (POCs) present in emissions from a diesel truck were characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The main compositions and molecular structures of WSOC and DMSOC were investigated and classified into three groups based on their elemental compositions: CHO, CHON, and S-containing compounds (CHONS and CHOS) (namely WSOCCHO; WSOCCHON; WSOCOS; DMSOCCHO; DMSOCCHON and DMSOCOS). The main results are as follows. (1) The order of groups in WSOC and DMSOC in terms of peak response was CHO (WSOC: 52.2% and DMSOC: 64.5%), CHON (WSOC: 43.4% and DMSOC:25.9%), and S-containing compounds (WSOC: 4.35% and DMSOC: 9.57%). (2) The relative response of compounds with low H/C and O/C ratios and double-bond equivalents (DBE) > 10 in WSOCCHO was twice that of DMSOCCHO, indicating that the WSOC emitted by diesel trucks might contain many highly condensed benzene rings. Compounds with H/C = 2 and DBE = 1 in DMSOCCHO showed a strong relative response, presumably due to a fatty-acid structure, which might be used as a tracer to distinguish emissions from diesel trucks and other pollution sources. (3) The strongest relative response in WSOCCHON was for C11H7O5N2 with an aromaticity equivalent (Xc) = 2.5 and DBE = 9, suggesting that dinitrophenol or methyl nitrophenol might be present. Moreover, C39H76O8N1 with Xc = 0 and DBE = 2 was dominant in DMSOCCHON, suggesting the presence of carboxylic acids. (4) In both WSOC and DMSOC, long-chain aliphatic and organic sulfate compounds accounted for the largest proportion of S-containing compounds. However, the contents of condensed hydrocarbons and aromatic rings in DMSOCOS were higher than those in WSOCOS, which suggests that DMSOCOS has a strong optical absorption ability. Thus, this study effectively determined the POC compounds of diesel truck emissions and their possible structures, providing data for assessing the environmental effects of using diesel trucks.

Compensation relationship in thermodynamics of vaporization of aromatic and aliphatic compounds and their heat capacities

It is long known that there is a correlation between the Gibbs energies and enthalpies of many processes, particularly solvation and vaporization, which is called the compensation relationship. Recently, we established that the correlation between the Gibbs energies and enthalpies of vaporization of non-hydrogen-bonded organic non-electrolytes at 298.15 K is divided into the two linear relationships with different slopes in the cases of aromatic and long-chain aliphatic compounds. We also recently found that there is a correlation between the difference between the heat capacities of the liquid and ideal gas, on the one hand, and the vaporization enthalpy at 298.15 K. Similarly with the compensation relationship, it is different in the cases of aromatic and aliphatic compounds.In this work, our goal was to establish the factors defining the values of the coefficients of the Gibbs energy-enthalpy correlation and understand its features in aromatic and aliphatic compounds. The thermodynamic analysis enabled to independently determine the coefficients of the compensation relationship, investigate their possible boundaries, and explicitly show how they depend on the difference between the heat capacities of the liquid and ideal gas and boiling entropy. Slight variations in the boiling entropy of non-hydrogen-bonded compounds appeared to have almost no effect on the compensation relationship, while the difference in the slopes exhibited by aromatic and aliphatic molecules was due to the features of the heat capacity-enthalpy dependence.

Alkane biosynthesis is promoted in methyl jasmonate-treated sweet cherry (Prunus avium) fruit cuticles.

The cuticle plays an important role in the survival of plants, and it is important to preserve the quality of fleshy fruits like sweet cherry. Plant hormones play a role in cuticle formation. In this sense, jasmonates have been shown to induce cuticle biosynthesis, but until today this has not been demonstrated in sweet cherry fruit. Therefore, the effect of exogenous methyl jasmonate (MeJA) application at the fruit set stage on the expression levels of cuticle synthesis-related genes and the wax composition of the isolated cuticle was studied in developing and ripe fruits of sweet cherry (Prunus avium 'Bing'), respectively. MeJA treatment resulted in up-regulation of the cuticle biosynthesis-related gene expression, such as PaWINA, PaWINB, PaKCS1, PaKCS6, PaLACS1, PaLACS2, PaWS, and PaWBC11. These genes play a vital role in the elongation and transport of fatty acids, and wax biosynthesis. Analysis of cuticular components in ripe fruit showed an increase in long-chain linear aliphatic wax compounds, particularly C27, C28, C29, C30, and C31 alkanes. Exogenous MeJA application at the fruit set stage of sweet cherry has a significant effect on the wax composition of the ripe fruit cuticle, particularly in terms of alkane biosynthesis. The results of this study may provide insights into the regulation of cuticle biosynthesis by jasmonates and be useful for improving fruit quality and storage life. © 2023 Society of Chemical Industry.

Effect of alkali and alkaline earth metals on the liquefaction of lignocellulosic model compounds to prepare bio-oil in ethanol solvent

In this paper, glucose, xylan and lignin were selected as typical components of lignocellulosic biomass to conduct liquefaction experiments, and the effect of alkali and alkaline earth metals (AAEMs) on biomass liquefaction in ethanol was investigated. Alkaline earth metals (AEMs) had a positive catalytic effect on the yield and quality of xylan liquefied bio-oil, in particular, MgCl2 increased the yield of bio-oil from 26.6 wt% to 38.8 wt%. AAEMs inhibited the formation of glucose and lignin bio-oil, the yield of bio-oil was changed from lignin > glucose > xylan to lignin > xylan > glucose. AAEMs increased the content of ester compounds in bio-oil, inhibited the formation of long-chain aliphatic compounds, and promoted the transformation of macromolecular aromatic compounds into coke. The active catalytic sites of AAEMs were gradually covered by the adsorption of residues and carbon free radicals, blocking the active sites. The ability of carbon free radical to capture H source was weakened, and the transfer of active hydrogen to bio-oil was inhibited, which was not conducive to the improvement of higher heating value (HHV) of bio-oil.

Value-added long-chain aliphatic compounds obtained through pyrolysis of phosphorylated chitin

In this work, chitin, as a biobased polymer, is used as a precursor to obtain a phosphorylated derivatives. The influence of the different degree of phosphorylation in chitin on pyrolysis pattern was investigated. In order to understand the pyrolysis mechanism and the potential application of phosphorylated chitins, the samples were pyrolyzed at different temperatures and analyzed by FTIR, SEM, and Py-GC/MS analysis. Moreover, the thermal degradation and the evolved gases during chitin degradation and its derivatives were measured. The results showed that phosphorylation of chitin decreased the thermal stability of biopolymer and significantly changed the pattern of pyrolysis compared to neat chitin. The production of long-chain hydrocarbons was detected during pyrolysis of phosphorylated chitin, whereas this was not the case with raw chitin. Those two effects were more pronounced as the degree of phosphorylation increased. Chitin with the degree of phosphorylation (DS 1.35) exhibited the highest selectivity (91 %) towards production of long-chain hydrocarbons (C12-C17) at 500 °C. Moreover, the obtained results allowed to propose, for the first time, the mechanism of pyrolysis of phosphorylated chitin.

Boron isotopes and FTIR spectroscopy to identify past high severity fires

Bushfires have played a crucial role in shaping the landscape and biodiversity for millennia. As fire regimes continue to alter with climate change, greater understanding becomes critical in mediating future events. Existing records are largely historically limited or do not accurately identify fire severity; therefore, there is a need to develop new proxies that can extend our fire records significantly. Here, we test whether changes in carbon (C) and nitrogen (N) content, boron (B) isotopes and Fourier Transform Infrared (FTIR) spectra in sediment deposits can identify past fire events. To achieve this, we investigated sediments deposited in small order creek beds of the Upper Nepean Catchment in southeastern Australia. In each deposit, layers associated with past fire events were independently identified based on visual inspection of higher charcoal abundance. Radiocarbon dating of charcoal fragments was used to approximate the age of the fire events.Neither C and N abundances nor C/N ratios show association with charcoal-rich layers, suggesting they are not useful proxies to identify past fires. Conversely, FTIR spectra show increased aromatic/aliphatic ratios in sediment layers recording past fire events. This observation suggests that those fires were hot enough to reduce long-chain aliphatic compounds to more temperature- and decomposition-resistant aromatics. In each deposit, an increase in δ11B by 2–7 ‰ is associated with charcoal-rich sediment layers. Leaves and fine branches, which burn only during high severity fires, are enriched in 11B, possibly causing the increase in the δ11B value of the sediment clay size fraction. These results suggest that, even in these small order creek beds which are typically transient environments, both FTIR spectra and B isotopes are potentially useful proxies to identify past fire events.

Crop rotational diversity alters the composition of stabilized soil organic matter compounds in soil physical fractions

Crop rotational diversity is an important part of sustainable agricultural and soil management to improve crop yield and soil fertility including enhancing soil organic matter (SOM) stabilization. Because of the physical protection via interactions with soil minerals, SOM in mineral-associated fractions is believed to be longer-lived and more stable relative to SOM in particulate (light) fractions. However, it is still unclear how crop rotational diversity alters soil carbon distribution, composition and stabilization in soil physical fractions. To address this, we studied a 37 years’ agricultural site with different crop rotational diversity (from continuous corn or alfalfa up to four species (corn, soybean, winter wheat, and red clover)). Soil carbon analysis, targeted compound analysis and nuclear magnetic resonance spectroscopy methods were used to obtain the distribution and degradation of SOM components in light and mineral-associated (F53–2000 µm, F2–53 µm, and F<2 µm) fractions. Higher soil organic carbon (SOC) concentrations were observed in F<2 µm with relatively high diversified crop rotations (three and four types of crops) compared to monoculture or two crops in the rotations, which suggests that carbon storage is enhanced in mineral-stabilized pools. Higher concentrations of long-chain aliphatic compounds as well as increased accumulation and preservation of lignin-derived compounds in fine aggregates (<53 µm) were also observed with relatively high diversified crop rotations. Overall, the increased concentration and preservation of specific SOM compounds as well as increased SOC in finer mineral-associated fractions (<53 µm) suggests that crop rotational diversity may enhance the long-term stability of SOM in agroecosystems.

Rosin acid and SiO2 modified cotton fabric to prepare fluorine-free durable superhydrophobic coating for oil-water separation

Currently, fluorides and long-chain aliphatic compounds are the most frequent low surface energy chemicals utilized in the preparation of superhydrophobic coatings, but associated environmental risks and instability restrict their potential application in oil-water separation. This research described a superhydrophobic coating based on rosin acid and SiO2 modified cotton fabric to overcome this challenge. By means of spray impregnation and UV-assisted click reaction, sulfhydryl modified rosin acid (RA), Octavinyl-POSS, and SiO2 were grafted onto the surface of cotton fabric to obtain RA-SiO2 superhydrophobic coating with rough surfaces such as lotus leaf and low surface energy. The RA-SiO2 superhydrophobic coating had favorable self-cleaning ability, and also adsorbed various light and heavy oils to achieve efficient separation of oil-water mixtures. The separation efficiency was 96.3% and the permeate flux was 6110.84 (L⋅m−2⋅h−1) after 10 repetitions. The RA-SiO2 superhydrophobic coating was found to be effective in separating oil-in-water and oil-in-water emulsions, and the separation mechanism was elaborated. In addition, it could effectively separate emulsions even after mechanical abrasion and chemical immersion, and had excellent stability. The fluorine-free and environmentally friendly low-cost superhydrophobic coating based on rosin acid is expected to play a significant potential in oil-water separation applications due to its excellent separation performance.

Structural characteristics of sediment humins from South Korean lakes and their phenanthrene binding compared to other carbon sources

Sediment humins are extremely important for binding hydrophobic organic contaminants in rivers and lakes. Nonetheless, little is known about their structure and binding. We, therefore, examined the structure and phenanthrene sorption affinity of sediment humin samples upstream, midstream, and downstream from two artificial lakes in South Korea by using the elemental 13C-NMR analysis, Freundlich model, and Langmuir model. The characteristics and phenanthrene sorption affinity of sediment humins were also compared with those of sediment humic acids from similar origins as well as soil humins/humic acids in South Korea from previous studies by using principal component analysis. In both lakes, downstream sediment humins exhibited lower N/C, O/C, and (N + O)/C ratios, lower internal oxidation, and higher aliphaticity due to the presence of long-chain aliphatic compounds generated during anaerobic decomposition. The principal component analysis results also showed that C,H-alkyl, O-alkyl, and polar organic carbon contents were significantly different when comparing the up-mid stream and downstream sediment samples in Daecheong Lake. In addition, midstream sediment humin in Andong Lake presented higher C,H-alkyl and lower polar organic carbon contents compared to those of up-downstream samples. In both lakes, the sorption coefficient and adsorption isotherm linearity were positively correlated with the C,H-alkyl content and negatively correlated with the O-aryl content. Similar to C,H-alkyl and POC, C,H-alkyl, and (N + O)/C had an extremely high correlation coefficient when predicting the sorption coefficient (Freundlich model) and the maximum adsorption capacity (Langmuir model) of sediment humins. Sediment humins had higher C,H-alkyl contents and lower sorption coefficients than those of sediment humic acids and soil humins/humic acids. These findings provide key information for monitoring water quality and polycyclic aromatic hydrocarbon contamination in South Korean lake sediments.

Abscisic acid applied to sweet cherry at fruit set increases amounts of cell wall and cuticular wax components at the ripe stage

Cuticle integrity represents an important factor in fruit quality of sweet cherries. Plants hormones, especially abscisic acid (ABA), are involved in fruit cuticle integrity. The effect of pre-harvest application of abscisic acid on cherry fruit cuticles was investigated. Changes of the concentrations of several phytohormones, expression levels of genes related to cell wall-modification, and to wax- and cutin biosynthesis were measured five days after applying ABA to sweet cherry trees (Prunus avium cv. Bing) at the stage of fruit set. At the ripe stage changes in cell wall polymers and fruit cuticle composition were measured. Our results show that pre-harvest application of 0.1 mM ABA at the stage of fruit set resulted in increased levels of zeatin ribose (204-fold), zeatin (126-fold), salicylic acid (30-fold), and ABA (19-fold). Transcription levels of key genes involved in cuticle biosynthesis, the transcription factor PaWINA and the wax biosynthesis-related enzyme PaLACS1 (5.8- and 3.4-fold increase), as well as for the key enzyme PaNCED1, involved in ABA biosynthesis (6.9-fold increase), were increased. At the ripe stage, contents of covalently-bound pectins and hemicelluloses were higher with a concomitant reduction of water-soluble polymers in ABA-treated fruits. Amounts of linear long-chain aliphatic wax compounds, especially C27, C29, and C31 alkanes, were increased (1.2-, 1.3- and 2.3-fold, respectively), whereas no effect of ABA on pentycylcic triterpenoids was observed. We conclude that ABA treatment of cherry trees at the stage of fruit set positively affects sweet cherry fruit quality at ripening by enforcing the cell wall and modifying the cuticle composition.

Composition, sun protective and antimicrobial activity of lipophilic bilberry (Vaccinium myrtillus L.) and lingonberry (Vaccinium vitis-idaea L.) extract fractions

Berries of the genus Vaccinium found in bogs and forest of Northern Europe are a valuable source of biologically active substances containing sterols, unsaturated fatty acids, flavanoids, anthocyanins. The presence of these compounds provides various health benefits of berry use – treatment of urinary tract inflammation, controls levels of sugar in the blood, improves cardiovascular health and reduces negative effects of oxidative stress caused by free radicals. The studied bilberry (Vaccinium myrtillus L.) and lingonberry (Vaccinium vitis-idaea L.) lipids were fractionated using normal-phase chromatography and they were found to contain fatty acids (oleic, linoleic acid), sterols (β-sitosterol), isoprenoids (ursolic and oleanolic acid) and different long-chain aliphatic compounds. The prepared extract fractions were tested for their sun protective factor and antimicrobial activity. Fractions containing high concentrations of phenolic acids (cinnamic acid, benzoic acid) were shown to have potential UV-B blocking activity, whereas the fractions with high sterol content effectively inhibited the growth of tested bacteria. These findings are empirical for the creation of natural nutraceutical and cosmeceutical functional ingredients.

Extraction of Fulvic Acid from Lignite and Characterization of Its Functional Groups.

Fulvic acid (FA) is a complex organic mixture composed of small molecules. The structure and composition of FA vary greatly because of the different raw materials used for preparing FA. In this work, FA was extracted from shallow low-rank lignite by hydrogen peroxide (H2O2) in a microwave field, and the functional groups of FA were characterized. The optimal extraction process was determined, with the H2O2 concentration being the key factor affecting the yield of FA. Thermogravimetric analysis showed that FA was mainly composed of low molecular weight and readily pyrolyzed compounds. As shown by Fourier transform infrared spectroscopy, in the process of FA extraction by H2O2 oxidation of lignite, the content of −COOH increased, long-chain aliphatic compounds decreased, stretching vibrations of aromatic ring skeletons disappeared, and aromatic ring substitution became mainly tri- or disubstitution. Fluorescence spectroscopy indicated that FA had a low degree of aromaticity. X-ray photoelectron spectroscopy qualitatively and quantitatively revealed that the main modes of carbon–oxygen bonding in FA were C–O–, COO–, and C=O. Thus, this study not only lays a foundation for studying the composition and structure of coal-based FA but also opens a new avenue for a clean and efficient utilization of lignite.

Avocado kernels, an industrial residue: a source of compounds with insecticidal activity against silverleaf whitefly.

Fruit processing waste, such as kernels (endocarp + seed) of avocado [Persea americana Mill. (Lauraceae)], could be used as raw material in the preparation of botanical insecticides. In light of this potential, this study assessed the insecticidal action of extracts and fractions from kernels of two avocado cultivars (Breda and Margarida) on Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) biotype B, an important pest species in tropical conditions. Ethanolic and aqueous extracts prepared from kernels of P. americana, regardless of the plant cultivar used, caused promising insecticidal activity to whitefly nymphs. Based on yield in crude extracts [10.32 and 9.85% (w/w), respectively, for cultivars Breda and Margarida], on the bioassay results with crude extracts and on the chemical profiles, the ethanolic extract of kernels of P. americana cv. Breda was chose for the continuation of the study. Thus, the ethanolic extract of kernels of cv. Breda (LC50 = 197.84ppm and LC90 = 567.19ppm) was selected and subjected to fractionation by the liquid-liquid partition technique. The hexane and dichloromethane fractions of this extract caused significant mortality of nymphs. The analysis using the ultraviolet (UV) and hydrogen nuclear magnetic resonance (1H NMR) showed the presence of long-chain aliphatic compounds (alkanols or acetogenins of Lauraceae), alkylfurans (or avocadofurans), and unsaturated fatty acids in these fractions, which are possibly related to bioactivity observed in B. tabaci, besides saccharides. The results show that kernels of P. americana are promising sources of compounds with insecticidal action for the control of B. tabaci biotype B, a great opportunity to transform environmental problems into eco-friendly solutions to agriculture.

Evolution of the functional groups/structures of biochar and heteroatoms during the pyrolysis of seaweed

Pyrolysis temperature is one of the main parameters affecting the properties of biochar and the composition of bio-oil during the pyrolysis of aquatic biomass such as seaweed. In this study, the evolution of the functional groups of biochar during seaweed pyrolysis was characterized with in situ diffuse reflectance infrared Fourier transform spectroscopy. The results showed that restructuring of the biochar was more pronounced at temperatures ranging from 230 to 290 °C, where the decomposition and pyrolysis of glucose crystals, polysaccharides and long-chain aliphatic compounds dominated. Fusion of the aromatic rings started and reached the equivalent of six fused rings at 500 °C and 12 fused benzene rings at 800 °C. Varying the pyrolysis temperature remarkably affected the distribution/transformation of the heteroatom in biochar and in the bio-oil formed. A large proportion of nitrogen in the original protein formed in seaweed was retained in the biochar, even at 800 °C. The sulfur species in the original sulfate polysaccharide form was transformed initially to Mg2K2(SO4)3 and then to MgO and CaS crystals. The oxygen content in the seaweed-derived biochar was rather high, as a significant portion of carbon was transferred into the tar fraction due to the aliphatic nature of seaweed.

FTIR and DSC Studies of Binary Mixtures of Long-Chain Aliphatic Compounds: Lauric Acid – Cetyl-trimethylammonium Bromide

Structural and thermal properties of a solid-state binary mixture of long-chain cationic and anionic surfactants (so-called catanionic complexes) composed of cetyltrimethyl-ammonium bromide, [H3C–(CH2)15–N+(CH3)3]Br−(CTAB), and saturated fatty acid (FA), CH3(CH2)12COOH (lauric acid, kC12), are studied. To clarify the effect of intermolecular interactions on the crystalline structure and phase transitions in this class of supramolecular compounds, the 1 : 1 kC12-CTAB binary mixture is investigated by means of X-ray diffraction, differential scanning calorimetry (DSC), and temperature-variable Fourier transform infrared spectroscopy (FTIR). Based on the comparison of the obtained results with those of other CTAB-FA binary mixtures with different alkyl chain length mismatches, the possible molecular packing in the crystal phase of CTAB-FA complexes and the mechanism of successive phase transitions in the condensed state are proposed.

Study of oily sludge pyrolysis combined with fine particle removal using a ceramic membrane in a fixed-bed reactor

Oil sludge is one of solid wastes that produced in the oil industry. Pyrolysis has been considered as an attractive technology for oil recovery. However, solid fine particles could be generated during process of oil sludge pyrolysis that could cause fouling and blockage in downstream equipment and connections. In this work, a ceramic membrane was used in the reactor to filter the fine particles in the product gas. The influence of temperatures on the component of pyrolysis gas and oil were also investigated by GC–MS and FT-IR. The results showed that the ceramic membrane can trap different ranges of particles. For the particle size less than 38 mm and 38–75 mm, the mass fraction obtained in the presence of the ceramic membrane is higher than that collected without the membrane (from 1.62 to 3.07% and from 20.84 to 22.85%). A maximum oil yield of 10.47% and oil recovery ratio of 52.95% were obtained at 500 °C. The GC–MS analysis of the pyrolysis oil showed that the oil was composed of long-chain aliphatic compounds with a number of carbons ranging from C10 − C27.

Structure-Dependent Hematological Effects of Per- and Polyfluoroalkyl Substances on Activation of Plasma Kallikrein-Kinin System Cascade.

Per- and polyfluoroalkyl substances (PFASs) are a global concern because of their ubiquitous occurrence and high persistence in human blood, and increasing amounts of unidentified fluorinated compounds are now becoming new exposure issues. This study aims to investigate the structure-related effects of PFASs on the activation of the plasma kallikrein-kinin system (KKS). The effects of 20 PFASs and the related long-chain aliphatic compounds were screened, and their binding affinities for the initial zymogen, Hagmen factor XII (FXII) in the KKS, were evaluated by molecular docking analysis. PFASs were demonstrated to activate the KKS in a structure-dependent mode. More specifically, PFASs with longer carbon chain length, higher fluorine atom substitution degree, and terminal acid group exhibited relatively higher activities in activating the KKS. The binding affinities of PFASs with FXII determined their capabilities for inducing KKS activation. The alternative binding modes of PFASs with FXII, together with van der Waals and hydrogen bonds, specifically accommodated the distinctive chemical structures. To our knowledge, PFASs, for the first time, were found to induce the activation of the KKS in plasma, and their chemical structure-related effects would be extremely important for risk assessment on emerging PFASs in addition to the listing in Stockholm Convention.

Aggregation behavior of TiO2 nanoparticles in municipal effluent: Influence of ionic strengthen and organic compounds

The influence of ionic strengthen and dissolved organic matter (DOM) on the aggregation of TiO2 nanoparticles (NPs) in municipal effluent was investigated. The results demonstrated that DOM promoted the mobility of NPs in aquatic system by synergism between static repulsion and steric effect, while electrolytes were opposite by charge-neutralization. The physical-chemical characteristics of DOM played the major role on the mobility of NPs. Bovine serum albumin (BSA) showed the strongest enhancement on the mobility of TiO2 NPs. High adsorption of BSA introduced vast negative charges on the TiO2 NPs' surface, leading to static repulsion and neutralizing positive charges of electrolytes in surrounding as well. By contrast, another protein α-amylase retarded the aggregation rate of TiO2 NPs through steric repulsion of the long-chain construction. Humic substances (Fulvic acid and alginate) also reflected the combination of static repulsion and steric effect. However, in the high electrolytes concentration (especially Ca2+), the long-chain aliphatic compounds were prone to form calcium bridge which increased the hydrodynamic diameter of TiO2 aggregates consequently. Sodium dodecylbenzene sulfonate (SDBS) showed low adsorption capacity, while the unabsorbed SDBS retarded the aggregates caused by the changes of pH and electrolytes. These data indicated that decreasing of DOC concentration in aqueous system was important to reduce the mobility and potential risk of NPs in aqueous system.

Complete genome sequence of Pseudomonas citronellolis P3B5, a candidate for microbial phyllo-remediation of hydrocarbon-contaminated sites.

Pseudomonas citronellolis is a Gram negative, motile gammaproteobacterium belonging to the order Pseudomonadales and the family Pseudomonadaceae. We isolated strain P3B5 from the phyllosphere of basil plants (Ocimum basilicum L.). Here we describe the physiology of this microorganism, its full genome sequence, and detailed annotation. The 6.95 Mbp genome contains 6071 predicted protein coding sequences and 96 RNA coding sequences. P. citronellolis has been the subject of many studies including the investigation of long-chain aliphatic compounds and terpene degradation. Plant leaves are covered by long-chain aliphates making up a waxy layer that is associated with the leaf cuticle. In addition, basil leaves are known to contain high amounts of terpenoid substances, hinting to a potential nutrient niche that might be exploited by P. citronellolis. Furthermore, the isolated strain exhibited resistance to several antibiotics. To evaluate the potential of this strain as source of transferable antibiotic resistance genes on raw consumed herbs we therefore investigated if those resistances are encoded on mobile genetic elements. The availability of the genome will be helpful for comparative genomics of the phylogenetically broad pseudomonads, in particular with the sequence of the P. citronellolis type strain PRJDB205 not yet publicly available. The genome is discussed with respect to a phyllosphere related lifestyle, aliphate and terpenoid degradation, and antibiotic resistance.Electronic supplementary materialThe online version of this article (doi:10.1186/s40793-016-0190-6) contains supplementary material, which is available to authorized users.