Aliphatic Acids Research Articles

Ag‐Catalyzed, Selectfluor‐Mediated External Acid‐Free Minisci Reaction in Aqueous Solution

AbstractA silver‐catalyzed Minisci‐type reaction is reported here. Alkylation of electron‐deficient N‐heterocycles is achieved in aqueous solution through decarboxylative cross‐coupling of aliphatic acids and N‐heteroarenes in open air without external Brønsted acid. Selectfluor is used as a mild oxidant. Different substituents on heterocycles and acids are tolerated. Primary and secondary alkyl could be introduced efficiently into the heteroarenes.

New insights into the bioaccessibility and metabolic fates of short-chain bioactive peptides in goat milk using the INFOGEST static digestion model and an improved data acquisition strategy

The metabolic fates of potentially bioactive short-chain peptides (SCPs; amino acid numbers between 2 and 4) in gastrointestinal digestion have received little attention due to their low concentration and broad suppression during high resolution mass spectrometry (HRMS) analysis. A tailored workflow integrating mesoporous magnetic solid phase extraction and a novel ion transmission strategy (data-dependent acquisition combined with both an inclusion list and an exclusion list followed by a data-independent acquisition) was used to profile the composition of SCPs during in vitro simulated digestion (LOQ 0.02 to 0.1 μg L-1). A total of 47 dipeptides, 59 tripeptides, and 21 tetrapeptides were identified and quantified from 0.01 to 27.84 mg L-1 (RSD ≤ 9.1%) based on parallel reaction monitoring and an internal standard method. The structural properties of stable SCPs resistant to intestinal digestion were determined by analysis of variance (p < 0.05), with a Pro residue at the C-terminal or penultimate position, a slightly greater negative charge at pH 7.0, and fewer C-terminal aliphatic and polar amino acids. SCPs' metabolic fates varied during digestion, but the overall trend of content change for either total or individual SCP increased as the digestion proceeded, and they were further assessed by a database-driven bioactivity search, which matched a wide variety of bioactivities with the predominance of dipeptidyl peptidase (DPP) IV and angiotensin-converting enzyme (ACE) inhibitors. This study facilitated the understanding of bioaccessibility of the food-derived SCPs and provided essential guidelines for the properties of conserved structure in vivo.

Hemetsberger–Knittel and Ketcham Synthesis of Heteropentalenes with Two (1:1), Three (1:2)/(2:1) and Four (2:2) Heteroatoms

The synthetic methods leading to furo[3,2-b]pyrroles and thiazolo [5,4-d]thiazoles are reviewed herein. Furo-, thieno- and seleno [3,2-b]pyrroles are related to heteropentalenes, containing two heteroatoms in the entire structure, one each per core. The synthetic approach follows the Hemetsberger–Knittel protocol covering three reaction steps—the nucleophilic substitution of halogen-containing aliphatic carboxylic acid esters, Knoevenagel condensation and, finally, thermolysis promoting the intramolecular cyclocondensation to O,N-heteropentalene. The Hemetsberger–Knittel reaction sequence is also known for the preparation of O,N-heteropentalenes with three heteroatoms (2:1) and their sulphur and selen heteroatoms containing structural analogues and bispyrroles. The synthetic approach towards thiazolo [5,4-d] thiazoles represents a more straightforward route, according to the Ketcham cyclocondensation. Proceeding with the Ketcham process is more challenging since it occurs stepwise and the formation of by-products is obvious. Thiazolo [5,4-d]thiazole is a representative of the aromatic heteropentalene with four heteroatoms in the structure—twinned N and S, two for each of the five-membered rings. The synthetic approaches towards those particular heteropentalnes have been chosen as a consequence of our ongoing research dealing with the design, synthesis and applications of substituted furo [3,2-b]pyrroles and thiazolo [5,4-d]thiazole-based derivatives. While the furopyrroles are known for their pharmacological activity, thiazolothiazoles have become of interest to materials science. We are aware that from a “bank” of existing compounds/procedures not all are presented in this review, and we apologise to respective groups whose research have not been objectively included.

Activation of cellulose with CO2 and/or H2O: Evolution of functionalities of the biochar and environmental impacts

CO2 and H2O are two important activators in production of activated carbon (AC) via physical activation method. They could oxidize the carbonaceous species in biochar or biomass via varied mechanisms and might also impact environments as well as the pore structures and evolution of functionalities of AC in different ways. In this study, the activations of the biochar from pyrolysis of cellulose with H2O, CO2 or mixed H2O/CO2 were performed. The results demonstrated that H2O as an activator led to higher weight loss than that of CO2 during the activation, originating from its higher efficiency for oxidation of the aliphatic structures in biochar to –OH and their further removal via deoxygenation or dehydration. Activation with CO2 made the AC more oxygen-rich, due to the retainment of abundant oxygen-containing functionalities, which suppressed further oxidation of carbon species and led to formation of main micropores. The higher capability of H2O for deoxygenation made the AC more carbon-rich with much more developed pore structures as well as higher proportion of mesopores and thus the superior capability for adsorption of phenol. In addition, during the activation in either CO2 or H2O, the unsaturated aldehyde/ketone and C-O-C structures was thermally more stable than lactones, saturated aliphatic acids and aliphatic aldehydes. The life cycle analysis (LCA) suggested that CO2 activation showed lower impact on environment by reducing emissions and consumption of fossil fuel.

Characterisation of Kastamonu honeys by palynological and physicochemical methods

Thirty-three honey samples were collected between 2017 and 2018 in Kastamonu Province, in order to characterise the palynological and physico-chemical properties of the honey produced in the western Black Sea region of Türkiye. Melissopalynological characteristics of the honey samples were determined based on the total pollen number in 10 g (TPN-10 g) along with the pollen taxa diversity. The physicochemical properties of the samples including humidity ratio, volatile organic compounds, total phenolic content, fructose/glucose ratio and hydroxymethylfurfural (HMF) content were determined using a refractometer, gas chromatography coupled with mass spectrometry (GC–MS), ultraviolet-visible spectrometry and high-performance liquid chromatography, respectively. Melissopalynological analysis revealed that the honey samples contain 49 taxa, of which 18 were determined at family level and 31 were determined at genus level. The most common taxon was Castanea sativa while the other important taxa were Apiaceae, Asteraceae, Amaranthaceae, Boraginaceae, Brassicaceae, Fabaceae and Lamiaceae. Eleven out of 33 honey samples were monofloral and the remaining 22 samples were multifloral. According to the TPN-10 g results of the honey samples, the total number of pollens in 10 g of Kastamonu honey was between 1051 and 325 108 pollen grains. The moisture ratio was obtained between 11.9 and 18.9% while the fructose + glucose values were between 35.84 and 84.1 g/100 g. HMF content varied between 0.38 and 21.31 ppm while the total phenolic content varied between 39.6 and 138.8 mg GAE/100 g. The GC–MS analysis revealed that the samples contain compounds belonging to the groups of aldehydes, aliphatic acid and its esters, alcohols, hydrocarbons, flavonoids, carboxylic acid and esters, ketones, and sugars.

Epoxidized isosorbide-based esters with long alkyl chains as efficient and enhanced thermal stability and migration resistance PVC plasticizers

The development of a bio-based plasticizer with good plasticizing performance, migration resistance, and thermal stability for polyvinyl chloride (PVC) is still a notable challenge due to the trade-off between molecular weight and compatibility. Herein, epoxidized isosorbide-based esters featuring multiple epoxy groups were prepared via the esterification of isosorbide with various aliphatic acids with C-18 alkyl chains (oleic acid, linoleic acid, and linolenic acid) followed by epoxidation. The resulting epoxidized isosorbide-based esters were utilized as PVC resin plasticizers, and the overall performance of these plasticized PVC specimens was investigated in detail. Moreover, the esterification reaction was optimized and 1-propylsulfonic-3-methylimidazolium hydrogensulfate ionic liquid was selected as the catalyst. After the reaction was complete, the ionic liquid and product were in separate phases, enabling facile catalyst recycling in a simple, convenient, and environmentally friendly process. The most superior plasticizing effect was achieved by epoxidized isosorbide linolenate (EGLA-ISB). In comparison to the PVC samples plasticized with dioctyl terephthalate (DOTP), those plasticized with EGLA-ISB demonstrated a 15-fold increase in thermal stability during isothermal testing (a PVC/50EGLA-ISB film had a low weight loss of approximately 1.5% after heating at 200 °C for 120 min). Furthermore, the initial thermal decomposition temperature of the PVC plasticized by EGLA-ISB increased by almost 40 °C (up to 306.9 °C) compared to pure PVC, and a higher elongation at break (387%) was also observed. The excellent performance of the PVC plasticized by EGLA-ISB was attributed to the C-18 alkyl chains and multiple epoxy groups of EGLA-ISB, which improved its PVC compatibility, enhanced the thermal stability of the PVC.

The combined addition of citric and aromatic organic acids to an acid soil prolongs phosphorus availability

AbstractThe role of organic acids (both aliphatic and aromatic) in increasing soil P availability is well established. However, the effect of the combined addition of aliphatic and aromatic organic acids on soil P availability is not well studied, which is particularly important when assessing the efficacy of heterogeneous natural organic acid sources, such as compost and biochar, on soil P availability based on their total abundance of organic acid compounds. In this study, some naturally occurring aliphatic (oxalic and citric) and aromatic (benzoic, 4‐hydroxybenzoic, and protocatechuic) organic acids were incubated with an acidic soil for up to 110 days and their effect on soil P availability (Olsen extractable P) and phosphorus buffering capacity (PBC) were studied. The aliphatic and aromatic organic acids were added as individual and combined treatments. The experimental results suggested that aliphatic organic acids were more effective in increasing Olsen extractable P and decreasing soil PBC when compared to aromatic organic acids. The effect of citric acid on increasing soil P availability was prolonged when applied in combination with aromatic organic acids. The contrasting chemical nature and complementary effect between aliphatic and aromatic organic acids were suggested as the reason for this phenomenon.

Enhanced production of itaconic acid from enzymatic hydrolysate of lignocellulosic biomass by recombinant Corynebacteriumglutamicum

Itaconic acid (IA) is a value-added chemical currently produced by Aspergillus terreus from edible glucose and starch but not from inedible lignocellulosic biomass owing to the high sensitivity to fermentation inhibitors present in the hydrolysate of lignocellulosic biomass. To produce IA from lignocellulosic biomass, a gram-positive bacterium, Corynebacterium glutamicum, with a high tolerance to fermentation inhibitors was metabolically engineered to express a fusion protein composed of cis-aconitate decarboxylase from A.terreus responsible for IA formation from cis-aconitate and a maltose-binding protein (malE) from Escherichia coli. The codon-optimized cadA_malE gene was expressed in C.glutamicum ATCC 13032, and the resulting recombinant strain produced IA from glucose. IA concentration increased 4.7-fold by the deletion of the ldh gene encoding lactate dehydrogenase. With the Δldh strain HKC2029, an 18-fold higher IA production was observed from enzymatic hydrolysate of kraft pulp as a model lignocellulosic biomass than from glucose (6.15 and 0.34 g/L, respectively). The enzymatic hydrolysate of kraft pulp contained various potential fermentation inhibitors involved in furan aldehydes, benzaldehydes, benzoic acids, cinnamic acid derivatives, and aliphatic acid. Whereas cinnamic acid derivatives severely inhibited IA production, furan aldehydes, benzoic acids, and aliphatic acid improved IA production at low concentrations. The present study suggests that lignocellulosic hydrolysate contains various potential fermentation inhibitors; however, some of them can serve as enhancers for microbial fermentation likely due to the changing of redox balance in the cell.

FORMATION OF LEATHER FILLED WITH MODIFIED SYNTAN AND TANIDE COMPOSITION

The technology of manufacturing leather material for the upper of shoes from semi-finished chrome tanning obtained from raw cow hides been has been developed. The technology at the filling-plasticization stage involves the use of a syntane-tanide composition modified with alkylcarboxyethanolamine of aliphatic acids of fraction C7–9. The filling and plasticizing composition includes syntanе BNS TU 17-06-165-89 and mimosa extract tanids with a content of the main substance of 81.7%. The semi-finished product is plasticized with Fosfol L-1301 emulsion of Cromogenia Units, S.A., Spain. Chemical reagents in the structure of the material are fixed by potassium alum modified with sodium formate. All previous and subsequent processes and operations are performed according to the industrial technology of the enterprise “Chinbar”. The resulting semi-finished product is characterized by a volumetric yield of 256 cm3/100 g of protein, a specific surface area of 71 m2/g, which are 8.0 and 11.0% higher than the industrial sample. Deformation properties of topographic areas and coefficients of uniformity of topographic areas of leather materials at loads of 10.0 MPa and rupture were calculated. At the same time, a more effective characteristic of the homogeneity of the material structure is the uniformity factor at a load of 10.0 MPa. The leather material obtained by the experimental technology has a uniformly oriented structure with an arithmetic average coefficient of uniformity of 1.0, and the industrial material has a transversely oriented structure with an arithmetic average coefficient of uniformity of 0.83. The advantage of the experimental material over the industrial one in terms of the complex of physico-chemical and technological properties and the coefficient of uniformity increases the efficiency of its use for the manufacture of leather products. The obtained leather material meets the requirements of DSTU 2726-94 “Leathers for shoe uppers. Specifications”.

Ozonation of Gabapentin in Water─Investigating Reaction Kinetics and Transformation Mechanisms of a Primary Amine Using Isotopically Labeled Ozone.

Aliphatic amines are abundant micropollutants in wastewater treatment plant effluents. In order to mitigate such micropollutants, ozonation is one of the most commonly employed advanced treatment processes. Current research regarding ozone efficiency is heavily focusing on reaction mechanisms of different contaminant groups, including structures with amine moieties as reactive sites. This study analyzes pH-dependent reaction kinetics and pathways of gabapentin (GBP), an aliphatic primary amine with an additional carboxylic acid group. The transformation pathway was elucidated applying a novel approach using isotopically labeled ozone (18O) and quantum chemistry calculations. While the direct reaction of GBP with ozone is highly pH-dependent and slow at pH 7 (13.7 M-1 s-1), the rate constant of the deprotonated species (1.76 × 105 M-1 s-1) is comparable to those of other amine compounds. Pathway analysis based on LC-MS/MS measurements revealed that ozonation of GBP leads to the formation of a carboxylic acid group and simultaneous nitrate formation, which was also observed in the case of the aliphatic amino acid glycine. Nitrate was formed with a yield of approximately 100%. Experiments with 18O-labeled ozone demonstrated that the intermediate aldehyde does most likely not include any oxygen originating from ozone. Furthermore, quantum chemistry calculations did not provide an explanation for the C-N scission during GBP ozonation without ozone involvement, although this reaction was slightly more favorable than for respective glycine and ethylamine reactions. Overall, this study contributes to a deeper understanding of reaction mechanisms of aliphatic primary amines during wastewater ozonation.

Aroma correlation assisted volatilome coupled network analysis strategy to unveil main aroma-active volatiles of Rosa roxburghii

To investigate the main aroma-active volatiles out from comprehensive chemical profile, we proposed an aroma correlation assisted volatilome coupled network analysis strategy and applied it to the study of Rosa roxburghii. Based on 475 detected volatiles with GC × GC-TOF/MS analysis, the volatilome was screened with both positive aroma activities and high contents to discover some aliphatic acids, alcohols, aldehydes and esters, terpenoids as well as some alkenes and ketones. Especially, a series of homologous C6- and C8- acids, alcohols, aldehydes, esters as well as some terpenoids like limonene take the predominant contributions to the aromas. Moreover, two aroma-active and aroma-contributing volatile groups including acid–aldehyde-alcohol-ester and terpenoid groups were clustered to integrally be responsible for the major aromas of R. roxburghii with network analysis. Additionally, the accumulation of C6- and C8-family homologous aliphatic volatiles was also elucidated with linoleic and linolenic acid derived pathways. This strategy is practical to investigate the main aroma-active volatiles based on volatilome.

Characterization of high value products in the side-stream of Laminaria hyperborea alginate production - Targeting the phenolic content

Sustainable production based on renewable biomass and efficient bioprocesses are important elements in the growing blue bioeconomy. The traditional Laminaria hyperborea alginate production disposes approximately 80 % of the raw material, ignoring large amounts of potential high-value products from the alga. Particularly, the leaf fraction of the seaweed is often disregarded. This study aimed to characterize high value products from the alginate production side-stream – focusing on the leaf biomass and particularly targeting the phenolic content. After extraction and solvent optimization, 60 % methanol was used for the extraction. The extract was further purified with PuriFlash and semi-preparative chromatography and increasing phenolic selectivity and purity was observed with TPC and qNMR, as well as antioxidant activity (ORAC). In the purified fractions, the LR LC-MS analyses displayed several masses, where 96 % (n = 1376) were of lower molecular weights (< 800 Da). Fifteen high value compounds were further identified using HR LC-MS (MS/MS) and/or NMR. This also included non-phenolics such as fucoxanthin, aliphatic acids and mannitol. Nonetheless, most compounds were identified as the targeted phenolics, consisting of lower molecular weight phenolic acids (salicylic acid, veratric acid, 5-caboxyvanillic acid, sinapic acid, 5-sulfosalicylic acid, vanillic acid 4-sulfate, and dihydrocaffeic acid 3-sulfate) and phlorotannins (trimer, tetramer, hexamer, and a sulfated dimer). None of the identified phenolics have previously been reported in L. hyperborea. In general, a high occurrence of sulfated phenolic compounds was observed and a sulfated diphlorethol/difucol was characterized for the first time. The isolation and characterization of high value components in the leaf biomass of L. hyperborea strongly supports the development of a total utilization of commercial alginate production. The characterization also adds information on the phenolic content of seaweeds at a molecular level, valuable to research on seaweed biosynthesis and development, chemical ecology, and ocean monitoring.

Matrix‐enhanced secondary ion mass spectrometry: Effects of aliphatic carboxylic acid matrices on the sensitivity enhancement of biological phospholipids

Matrix‐enhanced secondary ion mass spectrometry (ME‐SIMS) is an effective pre‐treatment method for the sensitivity enhancement of large molecules. Recently, matrix‐assisted laser desorption/ionization (MALDI) matrices, which consist of aromatic acids with benzene rings, have been developed using this technique. However, there are several differences in the desorption and ionization processes of SIMS and MALDI. In this study, the sensitivities of phospholipids mixed with aliphatic carboxylic acids were investigated using Bi‐cluster time‐of‐flight SIMS (TOF‐SIMS). Trans‐aconitic acid (tri‐carboxylic acid) and citric acid (hydroxycarboxylic acid) were used as the matrices. 2,5‐Dihydroxybenzoic acid (DHB), which is a typical aromatic MALDI matrix, was selected as the reference matrix. When trans‐aconitic acid and DHB were used as matrices, the secondary ion yields of [M + H]+ and [2 M + H]+ for phospholipids were approximately 10–150 times higher than that of the pristine lipid. For samples with citric acid, the yield enhancements of [M + H]+ and [2 M + H]+ were approximately 400–1000 times higher than those of pristine lipids. Furthermore, the protonated ionization of citric acid was mostly suppressed because of mixture with phospholipids. These results indicate that the matrix effect between phospholipids and the matrix contributes to the sensitivity enhancement of the target molecules. Hence, aliphatic carboxylic acid was equally or more effective than the MALDI matrix for the sensitivity enhancement of phospholipids in Bi‐cluster TOF‐SIMS.

In silico mutation of aromatic with aliphatic amino acid residues in Clostridium perfringens epsilon toxin (ETX) reduces its binding efficiency to Caprine Myelin and lymphocyte (MAL) protein receptors

Enterotoxaemia (ET) is a severe disease that affects domestic ruminants, including sheep and goats, and is caused by Clostridium perfringens type B and D strains. The disease is characterized by the production of Epsilon toxin (ETX), which has a significant impact on the farming industry due to its high lethality. The binding of ETX to the host cell receptor is crucial, but still poorly understood. Therefore, the structural features of goat Myelin and lymphocytic (MAL) protein were investigated and defined in this study. We induced the mutations in aromatic amino acid residues of ETX and substituted them with aliphatic residues at domains I and II. Subsequently, protein-protein interactions (PPI) were performed between ETX (wild)-MAL and ETX (mutated)-MAL protein predicting the domain sites of ETX structure. Further, molecular dynamics (MD) simulation studies were performed for both complexes to investigate the dynamic behavior of the proteins. The binding efficiency between ‘ETX (wild)-MAL protein’ and ‘ETX (mutated)-MAL protein complex’ interactions were compared and showed that the former had stronger interactions and binding efficiency due to the higher stability of the complex. The MD analysis showed destabilization and higher fluctuations in the PPI of the mutated heterodimeric ETX-MAL complex which is otherwise essential for its functional conformation. Such kind of interactions with mutated functional domains of ligands provided much-needed clarity in understanding the pre-pore complex formation of epsilon toxin with the MAL protein receptor of goats. The findings from this study would provide an impetus for designing a novel vaccine for Enterotoxaemia in goats. Communicated by Ramaswamy H. Sarma

Biobased composites of poly(butylene furanoate) copolymers and hemp

AbstractThere is growing interest in biodegradable and bio‐based materials that can replace conventional plastics in applications such as packaging. Polymers based on 2,5‐furandicarboxylic acid (FDCA) have been proposed as bio‐based analogues for polymers based on terephthalic acid. However, they tend to be brittle, exhibit limited biodegradability, and there are few examples of biocomposites from these polymers. Described here is the preparation of a small library of copolyesters based on FDCA, 1,4‐butanediol, and either succinic, adipic or sebacic acid. By incorporating different dicarboxylic acids in varying ratios, the glass transition temperature was tuned from −30 to 41°C and the melting temperature from 104–171°C while maintaining high stability up to ~300°C. Incorporation of aliphatic dicarboxylic acids facilitated blending of the copolymers with hemp powder, with up to 30 wt% hemp incorporated into the polymer containing 60:40 FDCA:sebacic acid. Incorporation of hemp did not substantially alter the thermal properties but increased the moduli of the composites. The copolyesters were susceptible to degradation by Rhizopus oryzae lipase, with the sebacic acid‐containing polyester having higher degradability than the succinic acid‐containing polyester. Overall, the results demonstrate the promise of the copolyester‐hemp blends for applications where they can replace conventional non‐degradable plastics.

RB-TnSeq identifies genetic targets for improved tolerance of Pseudomonas putida towards compounds relevant to lignin conversion

Lignin-derived mixtures intended for bioconversion commonly contain high concentrations of aromatic acids, aliphatic acids, and salts. The inherent toxicity of these chemicals places a significant bottleneck upon the effective use of microbial systems for the valorization of these mixtures. Pseudomonas putida KT2440 can tolerate stressful quantities of several lignin-related compounds, making this bacterium a promising host for converting these chemicals to valuable bioproducts. Nonetheless, further increasing P. putida tolerance to chemicals in lignin-rich substrates has the potential to improve bioprocess performance. Accordingly, we employed random barcoded transposon insertion sequencing (RB-TnSeq) to reveal genetic determinants in P. putida KT2440 that influence stress outcomes during exposure to representative constituents found in lignin-rich process streams. The fitness information obtained from the RB-TnSeq experiments informed engineering of strains via deletion or constitutive expression of several genes. Namely, ΔgacAS, ΔfleQ, ΔlapAB, ΔttgR::Ptac:ttgABC, Ptac:PP_1150:PP_1152, ΔrelA, and ΔPP_1430 mutants showed growth improvement in the presence of single compounds, and some also exhibited greater tolerance when grown using a complex chemical mixture representative of a lignin-rich chemical stream. Overall, this work demonstrates the successful implementation of a genome-scale screening tool for the identification of genes influencing stress tolerance against notable compounds within lignin-enriched chemical streams, and the genetic targets identified herein offer promising engineering targets for improving feedstock tolerance in lignin valorization strains of P. putida KT2440.

Relation of xylitol formation and lignocellulose degradation in yeast

One of the critical steps of the biotechnological production of xylitol from lignocellulosic biomass is the deconstruction of the plant cell wall. This step is crucial to the bioprocess once the solubilization of xylose from hemicellulose is allowed, which can be easily converted to xylitol by pentose-assimilating yeasts in a microaerobic environment. However, lignocellulosic toxic compounds formed/released during plant cell wall pretreatment, such as aliphatic acids, furans, and phenolic compounds, inhibit xylitol production during fermentation, reducing the fermentative performance of yeasts and impairing the bioprocess productivity. Although the toxicity of lignocellulosic inhibitors is one of the biggest bottlenecks of the biotechnological production of xylitol, most of the studies focus on how much xylitol production is inhibited but not how and where cells are affected. Understanding this mechanism is important in order to develop strategies to overcome lignocellulosic inhibitor toxicity. In this mini-review, we addressed how these inhibitors affect both yeast physiology and metabolism and consequently xylose-to-xylitol bioconversion. In addition, this work also addresses about cellular adaptation, one of the most relevant strategies to overcome lignocellulosic inhibitors toxicity, once it allows the development of robust and tolerant strains, contributing to the improvement of the microbial performance against hemicellulosic hydrolysates toxicity. KEY POINTS: • Impact of lignocellulosic inhibitors on the xylitol production by yeasts • Physiological and metabolic alterations provoked by lignocellulosic inhibitors • Cell adaptation as an efficient strategy to improve yeast's robustness.

Advanced biodegradable thermoplastic elastomer/reduced graphene oxide nanocomposites by in situ compositing process

AbstractIn this article, aliphatic diols (1,3‐propylene glycol and 1,4‐butanediol), aliphatic dibasic acids (succinic acid, sebacic acid, and fumaric acid), and graphene oxide (GO), were used as raw materials to prepare the advanced biodegradable thermoplastic elastomer (BTPE)/reduced GO (rGO) nanocomposites through reactions of in situ melting condensation, chemical reduction, and chain extension. The rGO is well dispersed in BTPE matrix by means of its predispersion in aliphatic diols before the polycondensation of the polyester prepolymers. Tensile strength of the BTPE/rGO nanocomposite with GO dosage of 0.6 wt% increase from 8.2 MPa of BTPE to 15.6 MPa, and its elongation at break also increases simultaneously. Meanwhile, biodegradability and electrical conductivity of the BTPE/rGO nanocomposites with GO dosage of 1.0 wt% increase greatly compared with those of BTPE. The advanced BTPE/rGO nanocomposites have great potential values in the fields of biodegradable medical materials, antistatic and conductive materials, among other applications.

Analysis, distribution and evolution of individual carboxylic acids in crude oil during biodegradation

Carboxylic acids (CAs) are important molecular markers in the study of petroleum biodegradation. This work presents a vortex-assisted liquid–liquid microextraction (VALLME) method, followed by comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC–MS) analysis for the profiling of CAs in complex oils. The designed extractant containing CAs in VALLME can be silylated immediately and injected into GC × GC–MS without any post-treatment. More than 400 individual CAs, including alkanoic acids, cyclic aliphatic acids and aromatic acids, were putatively or positively identified. With good reproducibility and high sensitivity, VALLME combined with GC × GC–MS was applied to investigate the distribution and evolution of individual CAs in crude oil during laboratory biodegradation. It was found that acyclic acids and monocyclic aliphatic/aromatic acids could be detected at all stages of oil biodegradation, while polycyclic aliphatic/aromatic acids could only be identified in oils at a relatively higher degree of biodegradation. In addition, the contents of each type of CA changed regularly during biodegradation. Targeted analysis on the distributions of individual acyclic acids showed that the abundance ratio of short chain to long chain n-alkanoic acids kept increasing during biodegradation, which might reflect the multiple origins of short chain n-alkanoic acids. Moreover, based on the distributions of pristanic/phytanic acid and pristane/phytane in oils with different biodegradation degrees, pristanic and phytanic acid seemed to be more susceptible to degradation compared to their hydrocarbon analogues, and pristane might be more susceptible to degradation in comparison to phytane.

Role of aerosol liquid water content on the production of dicarboxylic acids in the dust-laden air masses over the Arabian Sea: Implications for heterogeneous chemistry

Oxalic acid and the related organics are ubiquitous water-soluble constituents of ambient organic aerosols (OA). Their molecular distributions and relative abundances provide crucial insights on the secondary OA formation processes in the marine atmosphere and are important for understanding the cloud-aerosol interactions. Here, we measured the concentrations of dicarboxylic acids, pyruvic acid, ω-oxocarboxylic acids and α-dicarbonyls alongside aerosol chemical composition in the South Asian outflow to the Arabian Sea. Oxalic acid (C2) was the most abundant dicarboxylic acid followed by succinic (C4) and malonic (C3) acids; this distribution is typical of “less aged OA”. Oxalic acid levels correlated well with aerosol liquid water content (ALWC) and non-sea-salt (nss)-SO42− (a tracer of coal combustion influence), suggesting an important aqueous phase oxidation of successive higher homologs. This was inferred based on the prevailing inverse relationships between the relative abundances of oxalic acid in total aliphatic dicarboxylic acids and those of malonic, succinic, glutaric, adipic, and azelaic acids. Likewise, the concentrations of glyoxal (Gly: a major compound emitted from vehicular exhaust) and glyoxylic acid (ωC2) correlated strongly with C4, nss-Ca2+ (dust tracer) and elemental carbon (EC: a combustion tracer from biomass/fossil-fuels). These observations suggest gas/particle partitioning and subsequent aqueous phase oxidation of Gly to ωC2 and then elongation (oligomerization) to succinic acid associated with the mineral dust particles. This means relative abundances of anthropogenic SO42− in the dust-laden air masses govern the secondary OA formation over the Arabian Sea.