C4 Carboxylic Acids Research Articles

Superparamagnetic composites of lignin regenerated from ionic liquid solutions for the efficient and selective removal of cationic dyes

Magnetic lignin nanoparticles (MLNs) were prepared by inducing their self-assembly through lignin regeneration in the [N-methyl-2-pyrrolidone][C1–C4 carboxylic acid] ionic liquids ([NMP]ILs), which are low-cost protic ionic liquid. [NMP]ILs are self-assembling solvent that can enhance the adsorption capacity of MLNs to a greater degree than tetrahydrofuran or H2O. Additionally, the anion types of [NMP]IL greatly influence the physiochemical properties of MLNs. The MLNs prepared through self-assembly with [NMP][formate] (MLN/[NMP][For]) exhibited a higher maximum adsorption capacity (134.53 mg/g) than the [NMP]ILs of C2–C4 carboxylate anions. MLN/[NMP][For] demonstrated stable adsorption within a pH range of 6–10 or at high salt concentrations (0.01–0.5 mol/L), retaining over 80 % of its regeneration efficiency after 5 cycles. In addition, MLN/[NMP][For] selectively removed cationic dyes in mixed binary anionic–cationic dye solutions. This work demonstrated the feasibility of preparing magnetic biosorbents with good selectivity and stability though regeneration and by adjusting the anions of ionic liquids.

Selective photocatalytic oxidation of furfural to C4 compounds with metal-TS-1 zeolite

A series of metal-TS-1 zeolite catalysts were designed to selectively catalyze the photo oxidation of furfural to C4 carboxylic acid derivatives at ambient temperature and pressure. The photocatalytic preparation of malic acid from furfural was realized for the first time. The selective distribution of products could be controlled by adjusting the physical and chemical characteristics of the catalyst. Smaller pore size prevented the further conversion of maleic acid to malic acid; moderate acidity was beneficial for the preparation of malic acid; lower valence band was in favor of maleic acid production while higher valence band tended to form malic acid. The synergistic effect of pore structure, acidity and energy band structure of catalysts affected the product distribution. The yield of maleic acid reached as high as 40% over Fe-TS-1, meanwhile, the yield of malic acid reached as high as 63% over Ni-TS-1. The doping of metal was believed to be an effective procedure to adjust the structure and physicochemical properties of zeolite. Matel-TS-1 zeolite was also expected to be widely used in photocatalytic system to achieve more selective reactions.

Transcriptional regulation in key metabolic pathways of Actinobacillus succinogenes in the presence of electricity

The potential of renewable energy application via direct electrode interaction for the production of bio-based chemicals is a promising technology. The utilization of extracellular energy in pure culture fermentations aims in intracellular redox balance regulation in order to improve fermentation efficiency. This work evaluates the impact of a bioelectrochemical system in succinic acid fermentation and the metabolic response of Actinobacillus succinogenes. The metabolic pathway regulation of A. succinogenes was evaluated via RNA expression of the key enzymes that participate in TCA cycle, pyruvate metabolism and oxidative phosphorylation. The genes that were significantly overexpressed in BES compared to non-BES were phosphoenolpyruvate carboxykinase (0.4-fold change), inorganic pyrophosphatase (2.3-fold change) and hydrogenase (2.2-fold change) and the genes that were significantly underexpressed were fumarase (−0.94-fold change), pyruvate kinase (−6.9-fold change), all subunits of fumarate reductase (−2.1 to −1.17-fold change), cytochromes I and II (−1.25 and −1.02-fold change, respectively) and two C4-carboxylic acid transporters.

Nano-magnetite effects on CO2 reduction of homoacetogens with different extracellular electron transfer pathways

This study aimed to investigate the effect of nano-magnetite on the CO2 reduction of homoacetogens with different extracellular electron transfer (EET) pathways in the microbial electrosynthesis system (MES). Homoacetogens were cathode-cultured in the MES, which was operated under voltages of 0.5 and 0.8 V. Compared with the MES without magnetite, acetate (i.e., a C2–C4 carboxylic acid) yield was doubled in the MES with nano-magnetite under 0.5 V. However, the nano-magnetite effect was not significant in the MES under 0.8 V. The result suggested that homoacetogens in the MES had different EET pathways under different voltages. Based on SEM and CV results, magnetite promoted microorganism adherence to the cathode, and enhanced catalytic activity of the biocathode at 0.5 V, which increased acetate yield. Carbonyl cyanide m-chlorophenylhydrazone inhibited the ATP synthesis of homoacetogens in the H2-cultured condition but increased the current output in the biocathode, suggesting that the pathway for homoacetogens to harvest electrons from the cathode was different from the H2-mediated pathway. Rotenone inhibited the current output of biocathode at 0.5 V by 3.6% and 15% with and without nano-magnetite, respectively, indicating that NADH dehydrogenase played an important role on the EET pathways of homoacetogens.

Taxonomic and Functional Diversity of Rhizosphere Microbiome Recruited From Compost Synergistically Determined by Plant Species and Compost.

Compost is frequently served as the first reservoir for plants to recruit rhizosphere microbiome when used as growing substrate in the seedling nursery. In the present study, recruitment of rhizosphere microbiome from two composts by tomato, pepper, or maize was addressed by shotgun metagenomics and 16S rRNA amplicon sequencing. The 16S rRNA amplicon sequencing analysis showed that 41% of variation in the rhizosphere bacterial community was explained by compost, in contrast to 23% by plant species. Proteobacterial genera were commonly recruited by all three plant species with specific selections for Ralstonia by tomato and Enterobacteria by maize. These findings were confirmed by analysis of 16S rRNA retrieved from the shotgun metagenomics library. Approximately 70% of functional gene clusters differed more than sevenfold in abundance between rhizosphere and compost. Functional groups associated with the sensing and up-taking of C3 and C4 carboxylic acids, amino acids, monosaccharide, production of antimicrobial substances, and antibiotic resistance were over-represented in the rhizosphere. In summary, compost and plant species synergistically shaped the composition of the rhizosphere microbiome and selected for functional traits associated with the competition on root exudates.

Valorization of the organic fraction of municipal solid waste for fumaric acid production and electrochemical membrane extraction using Candida blankii

This work focuses on valorization of waste streams as crude renewable resources in the frame of the circular bioeconomy for C4-carboxylic acid production by the natural yeast Candida blankii. The metabolism of Candida blankii was affected by the availability of air due to fermentation conditions (agitation, total fermentation volume) resulting in direction of the carbon flux towards biomass or competing C4-dicarboxylic acid production. The maximum C4-dicarboxylic acid production was 69.1 g/L (fumaric acid was 45.8 g/L, malic acid was 21.6 g/L and succinic acid was 1.7 g/L) with 0.19 g/g yield and 0.27 g/L/h productivity. Candida blankii was able to consume a wide range of commercial carbon sources. The utilization of the organic fraction municipal solid waste hydrolysate resulted in the production of 37.6 g/L C4-dicarboxyic acids. Furthermore, electrolytic membrane extraction was used for the purification of the organic acids resulting in the reduction of downstream, separation and purification steps.

Lignin Syngas Bioconversion by Butyribacterium methylotrophicum: Advancing towards an Integrated Biorefinery

Hybrid bio-thermochemical based technologies have the potential to ensure greater feedstock flexibility for the production of bioenergy and bioproducts. This study focused on the bioconversion of syngas produced from low grade technical lignin to C2-/C4-carboxylic acids by Butyribacterium methylotrophicum. The effects of pH, medium supplementation and the use of crude syngas were analyzed. At pH 6.0, B. methylotrophicum consumed CO, CO2 and H2 simultaneously up to 87 mol% of carbon fixation, and the supplementation of the medium with acetate increased the production of butyrate by 6.3 times. In long-term bioreactor experiments, B. methylotrophicum produced 38.3 and 51.1 mM acetic acid and 0.7 and 2.0 mM butyric acid from synthetic and lignin syngas, respectively. Carbon fixation reached 83 and 88 mol%, respectively. The lignin syngas conversion rate decreased from 13.3 to 0.9 NmL/h throughout the assay. The appearance of a grayish pellet and cell aggregates after approximately 220 h was indicative of tar deposition. Nevertheless, the stressed cells remained metabolically active and maintained acetate and butyrate production from lignin syngas. The challenge that impurities represent in the bioconversion of crude syngas has a direct impact on syngas cleaning requirements and operation costs, supporting the pursuit for more robust and versatile acetogens.

Performance-advantaged ether diesel bioblendstock production by a priori design

Lignocellulosic biomass offers a renewable carbon source which can be anaerobically digested to produce short-chain carboxylic acids. Here, we assess fuel properties of oxygenates accessible from catalytic upgrading of these acids a priori for their potential to serve as diesel bioblendstocks. Ethers derived from C2 and C4 carboxylic acids are identified as advantaged fuel candidates with significantly improved ignition quality (>56% cetane number increase) and reduced sooting (>86% yield sooting index reduction) when compared to commercial petrodiesel. The prescreening process informed conversion pathway selection toward a C11 branched ether, 4-butoxyheptane, which showed promise for fuel performance and health- and safety-related attributes. A continuous, solvent-free production process was then developed using metal oxide acidic catalysts to provide improved thermal stability, water tolerance, and yields. Liter-scale production of 4-butoxyheptane enabled fuel property testing to confirm predicted fuel properties, while incorporation into petrodiesel at 20 vol % demonstrated 10% improvement in ignition quality and 20% reduction in intrinsic sooting tendency. Storage stability of the pure bioblendstock and 20 vol % blend was confirmed with a common fuel antioxidant, as was compatibility with elastomeric components within existing engine and fueling infrastructure. Technoeconomic analysis of the conversion process identified major cost drivers to guide further research and development. Life-cycle analysis determined the potential to reduce greenhouse gas emissions by 50 to 271% relative to petrodiesel, depending on treatment of coproducts.

Modeling the partitioning of organic chemical species in cloud phases with CLEPS (1.1)

Abstract. The new detailed aqueous-phase mechanism Cloud Explicit Physico-chemical Scheme (CLEPS 1.0), which describes the oxidation of isoprene-derived water-soluble organic compounds, is coupled with a warm microphysical module simulating the activation of aerosol particles into cloud droplets. CLEPS 1.0 was then extended to CLEPS 1.1 to include the chemistry of the newly added dicarboxylic acids dissolved from the particulate phase. The resulting coupled model allows the prediction of the aqueous-phase concentrations of chemical compounds originating from particle scavenging, mass transfer from the gas-phase and in-cloud aqueous chemical reactivity. The aim of the present study was more particularly to investigate the effect of particle scavenging on cloud chemistry. Several simulations were performed to assess the influence of various parameters on model predictions and to interpret long-term measurements conducted at the top of Puy de Dôme (PUY, France) in marine air masses. Specific attention was paid to carboxylic acids, whose predicted concentrations are on average in the lower range of the observations, with the exception of formic acid, which is rather overestimated in the model. The different sensitivity runs highlight the fact that formic and acetic acids mainly originate from the gas phase and have highly variable aqueous-phase reactivity depending on the cloud acidity, whereas C3–C4 carboxylic acids mainly originate from the particulate phase and are supersaturated in the cloud.

Simultaneous Enzyme/Whole‐Cell Biotransformation of C18 Ricinoleic Acid into (R)‐3‐Hydroxynonanoic Acid, 9‐Hydroxynonanoic Acid, and 1,9‐Nonanedioic Acid

AbstractRegiospecific oxyfunctionalization of renewable long chain fatty acids into industrially relevant C9 carboxylic acids has been investigated. One example was biocatalytic transformation of 10,12‐dihydroxyoctadecanoic acid, which was produced from ricinoleic acid ((9Z,12R)‐12‐hydroxyoctadec‐9‐enoic acid) by a fatty acid double bond hydratase, into (R)‐3‐hydroxynonanoic acid, 9‐hydroxynonanoic acid, and 1,9‐nonanedioic acid with a high conversion yield of ca. 70%. The biotransformation was driven by enzyme/whole‐cell biocatalysts, consisting of the esterase of Pseudomonas fluorescens and the recombinant Escherichia coli expressing the secondary alcohol dehydrogenase of Micrococcus luteus, the Baeyer‐Villiger monooxygenase of Pseudomonas putida KT2440 and the primary alcohol/aldehyde dehydrogenases of Acinetobacter sp. NCIMB9871. The high conversion yields and the high product formation rates over 20 U/g dry cells with insoluble reactants indicated that various (poly‐hydroxy) fatty acids could be converted into multi‐functional products via the simultaneous enzyme/whole‐cell biotransformations. This study will contribute to the enzyme‐based functionalization of hydrophobic substances.magnified image

Experimental and Theoretical Evidence for the Reactivity of Bound Intermediates in Ketonization of Carboxylic Acids and Consequences of Acid–Base Properties of Oxide Catalysts

Ketonization of carboxylic acids on metal oxides enables oxygen removal and the formation of new C–C bonds for increasing the energy density and chemical value of biomass-derived streams. Information about the surface coverages and reactivity of various bound species derived from acid reactants and the kinetic relevance of the elementary steps that activate reactants, form C–C bonds, and remove O atoms and how they depend on acid–base properties of surfaces and molecular properties of reactants is required to extend the range of ketonization catalytic practice. Here, we examine such matters for ketonization of C2–C4 carboxylic acids on monoclinic and tetragonal ZrO2 (ZrO2(m), ZrO2(t)) materials that are among the most active and widely used ketonization catalysts by combining kinetic, isotopic, spectroscopic, and theoretical methods. Ketonization turnovers require Zr–O acid–base pairs, and rates, normalized by the number of active sites determined by titration methods during catalysis, are slightly higher...

Production of 2-Hydroxyisobutyric Acid from Methanol by Methylobacterium extorquens AM1 Expressing (R)-3-Hydroxybutyryl Coenzyme A-Isomerizing Enzymes.

In this study, we genetically modified a methylotrophic bacterium in order to channel intermediates of its overflow metabolism to the C4 carboxylic acid 2-hydroxyisobutyric acid, a precursor of acrylic glass. This has implications for biotechnology, as it shows that reduced C1 substrates, such as methanol and formic acid, can be alternative feedstocks for producing today's commodities. We found that product titers and yields depend more on host physiology than on the activity of the introduced heterologous function modifying the overflow metabolism. In addition, we show that the fitness of recombinant strains substantially varies when they express orthologous genes from different origins. Further studies are needed to extend the overflow production phase in methylotrophic microorganisms for the implementation of biotechnological processes.

Simultaneous Enzyme/Whole-Cell Biotransformation of Plant Oils into C9 Carboxylic Acids

Oxyfunctionalization of plant oils such as olive oil and soybean oil into C9 carboxylic acids (e.g., n-nonanoic acid and 9-hydroxynonanoic acid) was investigated. The biotransformation was composed of hydrolysis of plant oils by the Thermomyces lanuginosus lipase (TLL) and C9–C10 double-bond cleavage in unsaturated fatty acids by a serial reaction of a fatty acid double bond-hydratase of Stenotrophomonas maltophilia, an alcohol dehydrogenase of Micrococcus luteus, and a Baeyer–Villiger monooxygenase (BVMO) of Pseudomonas putida KT2440 expressed in Escherichia coli. The newly cloned oleate hydratase allowed one to produce 10-hydroxyoctadecanoic acid and 10-hydroxyoctadec-12-enoic acid at a high rate from oleic acid and linoleic acid, respectively, which are major fatty acid constituents of many plant oils. Furthermore, overexpression of a long chain fatty acid transporter FadL in the recombinant E. coli led to a significant increase of whole-cell biotransformation rates of oleic acid and linoleic acid into...

Gut antibacterial effects of C7 and C9 carboxylic acids in the diet of piglets

The antibacterial effects of odd-numbered medium-chain fatty acids (MCFA), such as C7 and C9 carboxylic acids, are poorly described and, hence, their potential as a feed additive for weaned piglets has not been explored. First, the antimicrobial activity was tested in in vitro incubations simulating the digestion in the stomach (pH 3), duodenum (pH 5), and ileum (pH 7) at 0, 17.5, 35.0, and 70.0 mmol/L carboxylate and compared with even-numbered MCFA. All compounds showed a significant reduction of analyzed bacterial counts compared with the control, in many cases >2 log reduction up to complete disappearance, depending on pH and dose. At pH 3 and 5, C6 through C9 carboxylic acids were equally effective against coliforms, whereas C10 was less effective. The activity against lactobacilli and streptococci was higher at the lower pH and increased with chain length. The antimicrobial effects of C7 and C9 carboxylic acids were, in most cases, in between or, in one case, better than that of their respective neighboring even-numbered MCFA. Next, an equal mixture of C7 and C9 carboxylic acid was fed to weaned piglets at 0, 0.1, 0.2, and 0.4% carboxylic acids in the diet for 42 d (8 pen replicates with 6 pigs each). At d 13/14, 1 piglet per pen was sampled to determine major gastric and proximal and distal small intestinal bacterial groups and histomorphological characteristics. Numerical improvements of animal performance for all supplemented diets were observed (P > 0.05) and this corroborated with a trend for longer villi in the proximal small intestine (P = 0.082). The highest dose tended to reduce streptococci in the stomach contents (P = 0.079). In vitro, C7 and C9 carboxylic acids demonstrated clear and significant antibacterial effects against the major bacterial groups in the stomach and small intestine. In the postweaning performance trial, they showed potential to ameliorate performance.

DFT-D2 Study of the Adsorption of Bio-Oil Model Compounds in HZSM-5: C1–C4 Carboxylic Acids

C1–C4 primary carboxylic acids were selected as model compounds to observe the nature and stability of bio-oil adsorption in zeolite HZSM-5 via DFT-D2 theoretical calculation. Adsorptions with and without solvents of water, dimethyl sulfoxide, methanol, and ethanol were studied. The most stable adsorption configuration is hydrogen bonding (HB) through the carbonyl oxygen of acid over the Bronsted acid site of zeolite with the strong energies range from −133.2 to −154.8 kJ/mol. Partial transfer of the Bronsted proton to the acid was observed. Strength of intramolecular-zeolite acid site interaction increases in the order: carbonyl oxygen HB > hydroxyl oxygen HB > CH3 physisorption. The vdW interactions increase notably with the size of the acids. The adsorption energies are significantly reduced by solvation effect.

Cobalt pivalate complex as a catalyst for liquid phase oxidation of n-hexane

Catalytic properties of cobalt(II) pivalate complex as both individual and supported on mesoporous molecular sieves Si-KIT-6, Al-KIT-6, and Ce-KIT-6 were investigated in liquid-phase oxidation of n-hexane with molecular oxygen. This complex was shown to be an active and selective catalyst for the oxidation of n-C6H14 into C1–C4 carboxylic acids. The activity of Co(II) pivalate remains practically unchanged on heterogenizing the complex on molecular sieve supports. At the same time, its selectivity and resistance towards an oxidative degradation are slightly increased.

N-Methyl-2-pyrrolidone][C1-C4 carboxylic acid]: a novel solvent system with exceptional lignin solubility.

Novel solvent systems composed of N-methyl-2-pyrrolidone and C1-C4 carboxylic acid exhibit unique physicochemical properties, e.g. large polarity, low viscosity and excellent hydrogen bonding capacity, which have demonstrated excellent lignin solubility that outperforms conventional solvents and ionic liquids.

Effect of the morphology of polyethylene glycol esters on the distribution of C1–C4 carboxylic acids in the gas phase-sorbent system

The effect of the morphology of polymer films on the distribution of volatile C1–C4 carboxylic acids in the sorbent-gas system is discussed. The efficiency of sorption of vapors of formic, acetic, propionic, and butyric acids on films of polyethylene glycol esters of various structures formed on the electrodes of a piezoquartz resonator by means of static evaporation of a drop and immersion of the resonator into a sorbent solution is evaluated.

Active Site Inhibitors of HCV NS5B Polymerase. The Development and Pharmacophore of 2‐Thienyl‐5,6‐dihydroxypyrimidine‐4‐carboxylic Acid.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Active site inhibitors of HCV NS5B polymerase. The development and pharmacophore of 2-thienyl-5,6-dihydroxypyrimidine-4-carboxylic acid

5,6-Dihydroxypyrimidine-4-carboxylic acids are a promising series of hepatitis C virus (HCV) NS5B polymerase inhibitors that bind at the active site of the enzyme. Here we report a simple 2-thienyl substituted analogue that shows 10-fold improved activity over the original lead, and which allowed us to further delineate the key elements of the pharmacophore of this class of inhibitor. This work led to the identification of a trifluoromethyl acylsulfonamide group as a viable replacement for the C4 carboxylic acid in this series.