Showing papers on "Acetic acid published in 2010"
TL;DR: AC-SO3H exhibited comparable and even much higher catalytic activities than the commercial catalysts in the esterification of aliphatic acids with longer carbon chains such as hexanoic acids and decanoic acid, which may be due to the large specific surface area and mesoporous structures of the activated carbon.
Abstract: Sulfonated (SO(3)H-bearing) activated carbon (AC-SO(3)H) was synthesized by an aryl diazonium salt reduction process. The obtained material had a SO(3)H density of 0.64 mmol·g-1 and a specific surface area of 602 m2·g-1. The catalytic properties of AC-SO(3)H were compared with that of two commercial solid acid catalysts, Nafion NR50 and Amberlyst-15. In a 10-h esterification reaction of acetic acid with ethanol, the acid conversion with AC-SO(3)H (78%) was lower than that of Amberlyst-15 (86%), which could be attributed to the fact that the SO(3)H density of the sulfonated carbon was lower than that of Amberlyst-15 (4.60 mmol·g-1). However, AC-SO(3)H exhibited comparable and even much higher catalytic activities than the commercial catalysts in the esterification of aliphatic acids with longer carbon chains such as hexanoic acid and decanoic acid, which may be due to the large specific surface area and mesoporous structures of the activated carbon. The disadvantage of AC-SO(3)H is the leaching of SO(3)H group during the reactions.
278 citations
TL;DR: The increase of potassium concentration in the growth medium was found to improve the expression of maximal tolerance to acetic acid, consistent with the idea that the adequate manipulation of nutrient concentration of industrial growth medium can be an interesting strategy to surpass the deleterious effects of this weak acid in yeast cells.
Abstract: Acetic acid is a byproduct of Saccharomyces cerevisiae alcoholic fermentation. Together with high concentrations of ethanol and other toxic metabolites, acetic acid may contribute to fermentation arrest and reduced ethanol productivity. This weak acid is also a present in lignocellulosic hydrolysates, a highly interesting non-feedstock substrate in industrial biotechnology. Therefore, the better understanding of the molecular mechanisms underlying S. cerevisiae tolerance to acetic acid is essential for the rational selection of optimal fermentation conditions and the engineering of more robust industrial strains to be used in processes in which yeast is explored as cell factory. The yeast genes conferring protection against acetic acid were identified in this study at a genome-wide scale, based on the screening of the EUROSCARF haploid mutant collection for susceptibility phenotypes to this weak acid (concentrations in the range 70-110 mM, at pH 4.5). Approximately 650 determinants of tolerance to acetic acid were identified. Clustering of these acetic acid-resistance genes based on their biological function indicated an enrichment of genes involved in transcription, internal pH homeostasis, carbohydrate metabolism, cell wall assembly, biogenesis of mitochondria, ribosome and vacuole, and in the sensing, signalling and uptake of various nutrients in particular iron, potassium, glucose and amino acids. A correlation between increased resistance to acetic acid and the level of potassium in the growth medium was found. The activation of the Snf1p signalling pathway, involved in yeast response to glucose starvation, is demonstrated to occur in response to acetic acid stress but no evidence was obtained supporting the acetic acid-induced inhibition of glucose uptake. Approximately 490 of the 650 determinants of tolerance to acetic acid identified in this work are implicated, for the first time, in tolerance to this weak acid. These are novel candidate genes for genetic engineering to obtain more robust yeast strains against acetic acid toxicity. Among these genes there are number of transcription factors that are documented regulators of a large percentage of the genes found to exert protection against acetic acid thus being considered interesting targets for subsequent genetic engineering. The increase of potassium concentration in the growth medium was found to improve the expression of maximal tolerance to acetic acid, consistent with the idea that the adequate manipulation of nutrient concentration of industrial growth medium can be an interesting strategy to surpass the deleterious effects of this weak acid in yeast cells.
224 citations
TL;DR: Proton transfer in protic ionic liquids obtained by proton transfer from a common acid, acetic acid, to a range of amine bases of similar pK(a)(aq) values suggests that there is a clear distinction between the behaviour of simple primary vs. tertiary amines.
Abstract: Proton transfer in protic ionic liquids is poorly understood. Some acid/base proton transfer reactions do not proceed to the extent that is expected from ΔpKaaq data from aqueous solutions, yet some do. In this work we have investigated protic ionic liquids obtained by proton transfer from a common acid, acetic acid, to a range of amine bases of similar pKaaq values. Probe indicator observations, transport property data allowing the construction of Walden plots and computational studies all suggest that there is a clear distinction between the behaviour of simple primary vs. tertiary amines, the proton transfer being more complete in the former case than the latter. The origins of this seem to be related to the hydrogen bonding ability of the ammonium ions in providing a good solvating environment for the ions produced by the proton transfer.
222 citations
TL;DR: The results revealed that the inhibitory effect of acetic acid could be reduced by increasing media pH, thus confirming that the undissociated form of acetics acid is the inhibitORY form of the molecule.
Abstract: A current challenge of the cellulosic ethanol industry is the effect of inhibitors present in biomass hydrolysates. Acetic acid is an example of one such inhibitor that is released during the pretreatment of hemicellulose. This study examined the effect of acetic acid on the cofermentation of glucose and xylose under controlled pH conditions by Saccharomyces cerevisiae 424A(LNH-ST), a genetically engineered industrial yeast strain. Acetic acid concentrations of 7.5 and 15 g L−1, representing the range of concentrations expected in actual biomass hydrolysates, were tested under controlled pH conditions of 5, 5.5, and 6. The presence of acetic acid in the fermentation media led to a significant decrease in the observed maximum cell biomass concentration. Glucose- and xylose-specific consumption rates decreased as the acetic acid concentration increased, with the inhibitory effect being more severe for xylose consumption. The ethanol production rates also decreased when acetic acid was present, but ethanol metabolic yields increased under the same conditions. The results also revealed that the inhibitory effect of acetic acid could be reduced by increasing media pH, thus confirming that the undissociated form of acetic acid is the inhibitory form of the molecule.
210 citations
TL;DR: In order to use sugarcane bagasse as a substrate for lactic acid production, optimum conditions for acid hydrolysis of the bagasse were investigated and Lactococcus lactis IO-1 was detoxified through amberlite and supplemented with 7 g l(-1) of xylose and 7 g of yeast extract.
196 citations
TL;DR: A proof of principle for the potential of this metabolic engineering strategy to improve ethanol yields, eliminate glycerol production, and partially convert acetate, which is a well-known inhibitor of yeast performance in lignocellulosic hydrolysates, to ethanol.
Abstract: In anaerobic cultures of wild-type Saccharomyces cerevisiae, glycerol production is essential to reoxidize NADH produced in biosynthetic processes. Consequently, glycerol is a major by-product during anaerobic production of ethanol by S. cerevisiae, the single largest fermentation process in industrial biotechnology. The present study investigates the possibility of completely eliminating glycerol production by engineering S. cerevisiae such that it can reoxidize NADH by the reduction of acetic acid to ethanol via NADH-dependent reactions. Acetic acid is available at significant amounts in lignocellulosic hydrolysates of agricultural residues. Consistent with earlier studies, deletion of the two genes encoding NAD-dependent glycerol-3-phosphate dehydrogenase (GPD1 and GPD2) led to elimination of glycerol production and an inability to grow anaerobically. However, when the E. coli mhpF gene, encoding the acetylating NAD-dependent acetaldehyde dehydrogenase (EC 1.2.1.10; acetaldehyde + NAD+ + coenzyme A acetyl coenzyme A + NADH + H+), was expressed in the gpd1 gpd2 strain, anaerobic growth was restored by supplementation with 2.0 g liter–1 acetic acid. The stoichiometry of acetate consumption and growth was consistent with the complete replacement of glycerol formation by acetate reduction to ethanol as the mechanism for NADH reoxidation. This study provides a proof of principle for the potential of this metabolic engineering strategy to improve ethanol yields, eliminate glycerol production, and partially convert acetate, which is a well-known inhibitor of yeast performance in lignocellulosic hydrolysates, to ethanol. Further research should address the kinetic aspects of acetate reduction and the effect of the elimination of glycerol production on cellular robustness (e.g., osmotolerance).
194 citations
TL;DR: In this article, vanillin and acetic anhydride are subjected to the Perkin reaction and then hydrogenation to afford acetyldihydroferulic acid, which exhibits thermal properties functionally similar to those of polyethylene terephthalate (PET).
191 citations
TL;DR: In this paper, different mixed oxide catalysts have been used to obtain acrylic acid directly from glycerol using different techniques (XRD, SEM, BET and TGA-DSC).
182 citations
TL;DR: In this paper, a comparative study of the adsorption and photoinduced degradation of acetone and acetic acid on thin films of anatase, brookite, and rutile TiO2 nanoparticles is presented.
Abstract: A comparative study of the adsorption and photoinduced degradation (PID) of acetone and acetic acid on thin films of anatase, brookite, and rutile TiO2 nanoparticles is presented. The materials were thoroughly characterized by a wide range of methods, including X-ray diffraction, transmission electron microscopy, and Raman and UV−vis spectroscopies. In situ FTIR transmission spectroscopy was used to follow adsorption and PID reactions. Molecular adsorption of acetone and acetic acid is observed on anatase and brookite, whereas significant dissociation occurs on rutile. It is inferred that adsorbate−surface interaction increases in the order anatase < brookite < rutile, favoring formation of bridge-bonded species on rutile (acetate and formate). Illumination with simulated solar light readily dissociates acetic acid and acetone on all TiO2 samples and produces polymorph-specific intermediate surface species, including acetate, formate, carbonate, and water. PID of surface coordinated acetate is rate determ...
167 citations
TL;DR: In this article, sulfonation of swelling mesoporous polydivinylbenzenes (PDVB- x s) by chlorosulfonic acid in CH 2 Cl 2 was used to synthesize efficient and stable solid acid catalysts.
159 citations
TL;DR: New 1-adamanyl-1,3,4-thiadiazole derivatives, synthesized and tested for in vitro activities against a panel of gram-positive and gram-negative bacteria and the yeast-like pathogenic fungus Candida albicans, produced good dose-dependent anti-inflammatory activity.
TL;DR: This mini-review focuses on the molecular properties of PQQ-ADH, such as the roles of the subunits and the cofactors, particularly in intramolecular electron transport of the enzyme from ethanol to Q.
Abstract: Pyrroquinoline quinone-dependent alcohol dehydrogenase (PQQ-ADH) of acetic acid bacteria is a membrane-bound enzyme involved in the acetic acid fermentation by oxidizing ethanol to acetaldehyde coupling with reduction of membranous ubiquinone (Q), which is, in turn, re-oxidized by ubiquinol oxidase, reducing oxygen to water. PQQ-ADHs seem to have co-evolved with the organisms fitting to their own habitats. The enzyme consists of three subunits and has a pyrroloquinoline quinone, 4 heme c moieties, and a tightly bound Q as the electron transfer mediators. Biochemical, genetic, and electrochemical studies have revealed the unique properties of PQQ-ADH since it was purified in 1978. The enzyme is unique to have ubiquinol oxidation activity in addition to Q reduction. This mini-review focuses on the molecular properties of PQQ-ADH, such as the roles of the subunits and the cofactors, particularly in intramolecular electron transport of the enzyme from ethanol to Q. Also, we summarize biotechnological applications of PQQ-ADH as to enantiospecific oxidations for production of the valuable chemicals and bioelectrocatalysis for sensors and fuel cells using indirect and direct electron transfer technologies and discuss unsolved issues and future prospects related to this elaborate enzyme.
TL;DR: In this paper, a one-step recovery of the desired product succinic acid crystal from the fermentation broths was studied for the first time, and the results showed that succinogenes BE-1 achieved a yield of 70% and purity of 90%.
TL;DR: The Lactobacillus plantarum strain was isolated from grass silage that produces a broad spectrum of antifungal compound, active against food and feed-borne filamentous fungi in agar plate assay, and acted as a fungistatic and delayed the growth of a variety of fungal contaminants.
Abstract: The Lactobacillus plantarum strain was isolated from grass silage that produces a broad spectrum of antifungal compound, active against food and feed-borne filamentous fungi in agar plate assay. Aspergillus fumigatus and Rhizopus stolonifer were the most sensitive among molds. No inhibitory activity could be detected against mold Penicillium roqueforti. Enhanced antifungal activity was observed at 30 °C in pH 6.5. Minimum inhibitory concentration values against fungal cultures were ranged from 6.5 to 12.0 mg/ml for commercial 3-phenyllactic acid. The production of antifungal compound phenyllactic acid (PLA), lactic acid, and acetic acid by L. plantarum strain was also investigated. Structure characterization of the antifungal compound was carried out by nuclear magnetic resonance spectroscopy, infrared spectroscopy, and gas chromatography. The produced compound (PLA) acted as a fungistatic and delayed the growth of a variety of fungal contaminants.
TL;DR: In this paper, the concentrations of acetic acid and formic acid vapours emitted by a number of wood samples held in sealed environments were measured to assess differences between hardwood and softwood species.
Patent•
26 Oct 2010TL;DR: In this article, a process for selective formation of ethanol from acetic acid by hydrogenating acetic acids in the presence of a catalyst comprises a first metal on an acidic support, which is used alone to produced ethanol via hydrogenation or in combination with another catalyst.
Abstract: A process for selective formation of ethanol from acetic acid by hydrogenating acetic acid in the presence of a catalyst comprises a first metal on an acidic support. The acidic support may comprise an acidic support material or may comprise an support having an acidic support modifier. The catalyst may be used alone to produced ethanol via hydrogenation or in combination with another catalyst. In addition, the crude ethanol product is separated to obtain ethanol.
TL;DR: In this paper, the authors showed that the glycerol conversion and selectivities depend on the acidity of the catalysts, which in turn is related to the content of TPA on niobic acid.
TL;DR: The use of methyl acetate instead of methanol for supercritical synthesis of glycerol-free biodiesel from vegetable oils is a new process and its study is very limited in the literature as mentioned in this paper.
TL;DR: In conclusion, this research has provided insights into molecular response to furfural and acetic acid in S. cerevisiae, and it will be helpful to construct more resistant strains for cellulosic ethanol production.
Abstract: Furfural and acetic acid are two prevalent inhibitors to microorganisms during cellulosic ethanol production, but molecular mechanisms of tolerance to these inhibitors are still unclear. In this study, genome-wide transcriptional responses to furfural and acetic acid were investigated in Saccharomyces cerevisiae using microarray analysis. We found that 103 and 227 genes were differentially expressed in the response to furfural and acetic acid, respectively. Furfural downregulated genes related to transcriptional control and translational control, while it upregulated stress-responsive genes. Furthermore, furfural also interrupted the transcription of genes involved in metabolism of essential chemicals, such as etrahydrofolate, spermidine, spermine, and riboflavin monophosphate. Acetic acid downregulated genes encoding mitochondrial ribosomal proteins and genes involved in carbohydrate metabolism and regulation and upregulated genes related to amino acid metabolism. The results revealed that furfural and acetic acid had effects on multiple aspects of cellular metabolism on the transcriptional level and that mitochondria might play important roles in response to both furfural and acetic acid. This research has provided insights into molecular response to furfural and acetic acid in S. cerevisiae, and it will be helpful to construct more resistant strains for cellulosic ethanol production.
TL;DR: Higher temperature, higher acid concentration and longer residence time all favor the depolymerization of hemicellulose wood extracts, mainly xylose and acetic acid are recovered from the hydrolysis process.
Journal Article•
TL;DR: In this article, it was shown that the initial CO bond scission yielding acetyl is the key step and that the intrinsic reactivity of the metals accounts for the observed activity.
Abstract: Catalytic hydrogenation of acetic acid to ethanol has been carried out in aqueous phase on several metals, with ruthenium being the most active and selective. DFT calculations suggest that the initial CO bond scission yielding acetyl is the key step and that the intrinsic reactivity of the metals accounts for the observed activity.
TL;DR: This work studied the concentration of hydrolyzates obtained from dilute acid hydrolysis of rice straw using nanofiltration (NF) in order to minimize the Donnan exclusion effect of the membrane, the Hydrolyzate solution was controlled at low pH value.
TL;DR: In this article, a series of propylsulfonic (MCM-SOH) and octyl co-functionalised propyl Sulfonic catalysts have been prepared by post modification of MCM-41 with mercaptopropyltrimethoxysilane (MPTS) to achieve SOH surface coverages spanning the range 0.12-1 monolayer.
TL;DR: In this article, the microwave-assisted pretreatment method was adopted to treat rice straw as an alternative to conventional pretreatment methods, and the product was further hydrolyzed by cellulase.
TL;DR: In this paper, the reaction of benzene, palladium chloride and sodium acetate in acetic acid solvent produces biphenyl in a high yield in the absence of sodiumacetate no reaction occurs.
Abstract: Reaction of benzene, palladium chloride and sodium acetate in acetic acid solvent produces biphenyl in a high yield. In the absence of sodium acetate no reaction occurs. The reaction is first-order with respect to benzene and PdCl2. With monosubstituted benzenes in general a mixture of isomeric biphenyls (X-C6H4-C6H4-X,X = alkyl, aryl, OR, Cl, COOR) is obtained. The substitution pattern corresponds with that observed in electrophilic aromatic substitution. The substituents exert a weak polar effect: electron-donating groups increase the rate, while the opposite holds for electron-attracting groups.
With disubstituted benzenes steric effects play an important role. From o-xylene 3,4,3′,4′- and 2,3,3′,4′-tetramethylbiphenyl have been obtained as the only products in a molar ratio of 2.7 : 1.
The results are most satisfactorily described by a mechanism involving complex formation between the aromatic compound and PdCl2 as the rate-determining step. The complex formed is assumed to yield a π-cyclohexadienyl-PdCl complex by a fast reaction with acetate anions. The complex formed, being unstable, decomposes to yield biphenyl and palladium metal.
TL;DR: In this paper, the conversion of glycerol in supercritical water (SCW) was studied at 510 - 550°C and a pressure of 350 bars using both a bed of inert and non-porous ZrO2 particles (hydrothermal experiments), and a 1 % Ru/ZrO 2 catalyst particles.
TL;DR: This class of compounds presented high potency against Staphylococcus aureus, among which the derivatives 5k with a MIC of 2 μg/mL was as active as the standard drug (norfloxacin) and less active than oxacillin.
TL;DR: It was found that acetic acid in hydrolysate inhibited the growth of K. oxytoca while benefited the 2,3-butanediol yield and the aceticacid inhibition on cell growth can be alleviated by adjusting pH to 6.3 prior to fermentation and a substrate fed-batch strategy with a low initial acetic Acid concentration.
TL;DR: In this article, it was shown that the initial CO bond scission yielding acetyl is the key step and that the intrinsic reactivity of the metals accounts for the observed activity.
Abstract: Catalytic hydrogenation of acetic acid to ethanol has been carried out in aqueous phase on several metals, with ruthenium being the most active and selective. DFT calculations suggest that the initial CO bond scission yielding acetyl is the key step and that the intrinsic reactivity of the metals accounts for the observed activity.
TL;DR: In this article, a study of the atmospheric heterogeneous reactions of formic acid, acetic acid, and propionic acid on α-Al2O3 was performed at ambient condition by using a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reactor.
Abstract: . A study of the atmospheric heterogeneous reactions of formic acid, acetic acid, and propionic acid on α-Al2O3 was performed at ambient condition by using a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reactor. From the analysis of the spectral features, observations of carboxylates formation provide strong evidence for an efficient reactive uptake process. Comparison of the calculated and experimental vibrational frequencies of adsorbed carboxylates establishes the bridging coordinated structures on the surface. The uptake coefficients of formic acid, acetic acid, and propionic acid on α-Al2O3 particles are (2.07±0.26)×10−3 or (2.37±0.30) ×10−7, (5.00±0.69)×10−3 or (5.99±0.78)×10−7, and (3.04±0.63)×10−3 or (3.03±0.52)×10−7, respectively (using geometric or BET surface area). Furthermore, the effect of varying relative humidity (RH) on these heterogeneous reactions was studied. The uptake coefficients of monocarboxylic acids on α-Al2O3 particles increase initially (RH 20%) which was due to the effect of water on carboxylic acid solvation, particle surface hydroxylation, and competition for reactive sites. On the basis of the results of experimental simulation, the mechanism of heterogeneous reaction of α-Al2O3 with carboxylic acids at ambient RH was discussed. The loss of atmospheric monocarboxylic acids due to reactive uptake on available mineral dust particles may be competitive with homogeneous loss pathways, especially in dusty urban and desertified environments.