Showing papers on "Acetic acid published in 2014"

Functional properties of vinegar.

Abstract: A variety of natural vinegar products are found in civilizations around the world. A review of research on these fermented products indicates numerous reports of health benefits derived by consumption of vinegar components. Therapeutic effects of vinegar arising from consuming the inherent bioactive components including acetic acid, gallic acid, catechin, ephicatechin, chlorogenic acid, caffeic acid, p-coumaric acid, and ferulic acid cause antioxidative, antidiabetic, antimicrobial, antitumor, antiobesity, antihypertensive, and cholesterol-lowering responses. The aims of this article are to discuss vinegar history, production, varieties, acetic acid bacteria, and functional properties of vinegars.

Iridium-catalyzed direct C-H amidation with weakly coordinating carbonyl directing groups under mild conditions.

Abstract: An iridium-catalyzed direct C-H amidation of weakly coordinating substrates, in particular of those bearing ester and ketone groups, under very mild conditions has been developed. The observed high reaction efficiency was achieved by the combined use of acetic acid and lithium carbonate as additives.

A four-component synthetic attractant for Drosophila suzukii (Diptera: Drosophilidae) isolated from fermented bait headspace.

Abstract: BACKGROUND A mixture of wine and vinegar is more attractive than wine or vinegar to spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), and ethanol and acetic acid are considered key to that attractiveness. In addition to ethanol and acetic acid, 13 other wine and vinegar volatiles are antennally active to D. suzukii and might be involved in food finding. RESULTS Out of the 13 antennally active chemicals, acetoin, ethyl lactate and methionol increased fly response to a mixture of acetic acid and ethanol in field trapping experiments. A five-component blend of acetic acid, ethanol, acetoin, ethyl lactate and methionol was as attractive as the starting mixture of wine and vinegar in field tests conducted in the states of Oregon and Mississippi. Subtracting ethyl lactate from the five-component blend did not reduce the captures of flies in the trap. However, subtracting any other compound from the blend significantly reduced the numbers of flies captured. CONCLUSION These results indicate that acetic acid, ethanol, acetoin and methionol are key olfactory cues for D. suzukii when attracted to wine and vinegar, which may be food-finding behavior leading flies to fermenting fruit in nature. It is anticipated that this four-component blend can be used as a highly attractive chemical lure for detection and management of D. suzukii. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Effect of dilute acid pretreatment conditions and washing on the production of inhibitors and on recovery of sugars during wheat straw enzymatic hydrolysis

Abstract: Pretreatment is an essential process to break down recalcitrant biomass and dilute acid hydrolysis is one of the most efficient and cost effective pretreatment technologies available today. However there are potential disadvantages in using dilute acid as a pretreatment, such as the production of degradation products, which inhibits the ensuing processing chain and limits its adoption. In this work, wheat straw was pretreated under varying dilute acid conditions; the resulting degradation products were determined and the quality of sugar stream generated via enzymatic saccharification was monitored. The dilute acid pretreatment conditions were: temperatures of 140 and 160 °C, sulfuric acid concentrations of 5, 10 and 20 dm3 m−3 and reaction times of 10, 20, 30, 45 and 60 min. Pretreated wheat straw was washed with six dilutions of water and hydrolyzed with commercial cellulase enzymes for 24–48 h. Optimal conditions for pretreating wheat straw were determined as: 140 °C, 10 dm3 m−3 sulfuric acid concentration and a 30 min reaction time. At these conditions, the glucose yield from wheat straw was maximized at 89% of the theoretical maximum, while the concentrations of formic acid, furfural, acetic acid and 5-hydroxymethylfurfural were 32.37 ± 4.91, 12.08 ± 1.69, 7.98 ± 1.02 and 1.14 ± 0.22 g kg−1, respectively. Increases in pretreatment severity led to increases in inhibitor generation, as well as a 27% reduction in monosaccharide yield. Rinsing with deionized water was effective in removing inhibitors, such as 86% of furfural. The formation of inhibitors was thus observed to depend on dilute acid pretreatment conditions.

Electrolytic Membrane Extraction Enables Production of Fine Chemicals from Biorefinery Sidestreams

Abstract: Short-chain carboxylates such as acetate are easily produced through mixed culture fermentation of many biological waste streams, although routinely digested to biogas and combusted rather than harvested. We developed a pipeline to extract and upgrade short-chain carboxylates to esters via membrane electrolysis and biphasic esterification. Carboxylate-rich broths are electrolyzed in a cathodic chamber from which anions flux across an anion exchange membrane into an anodic chamber, resulting in a clean acid concentrate with neither solids nor biomass. Next, the aqueous carboxylic acid concentrate reacts with added alcohol in a water-excluding phase to generate volatile esters. In a batch extraction, 96 ± 1.6% of the total acetate was extracted in 48 h from biorefinery thin stillage (5 g L(-1) acetate) at 379 g m(-2) d(-1) (36% Coulombic efficiency). With continuously regenerated thin stillage, the anolyte was concentrated to 14 g/L acetic acid, and converted at 2.64 g (acetate) L(-1) h(-1) in the first hour to ethyl acetate by the addition of excess ethanol and heating to 70 °C, with a final total conversion of 58 ± 3%. This processing pipeline enables direct production of fine chemicals following undefined mixed culture fermentation, embedding carbon in industrial chemicals rather than returning them to the atmosphere as carbon dioxide.

Chitosan: An Efficient, Reusable, and Biodegradable Catalyst for Green Synthesis of Heterocycles

Abstract: A convenient and rapid method is described for the synthesis of nitrogen heterocyclic derivatives by one-pot three-component reaction of substituted aromatic aldehydes, dicarbonyl- and 2-aminobenzothiazole/3-amino-1,2,4-triazole/urea/thiourea using commercially available chitosan in 2% acetic acid in aqueous media at 60–65 °C. Chitosan was used as an efficient biodegradable and reusable green catalyst for this multicomponent reaction. The chitosan catalyst can be reused 10 times in fresh reaction. Catalytic activity has been sustained in the first five runs but slightly decreased in subsequent cycles.

Oxidation of Metabolites Highlights the Microbial Interactions and Role of Acetobacter pasteurianus during Cocoa Bean Fermentation

Abstract: Four cocoa-specific acetic acid bacterium (AAB) strains, namely, Acetobacter pasteurianus 386B, Acetobacter ghanensis LMG 23848(T), Acetobacter fabarum LMG 24244(T), and Acetobacter senegalensis 108B, were analyzed kinetically and metabolically during monoculture laboratory fermentations. A cocoa pulp simulation medium (CPSM) for AAB, containing ethanol, lactic acid, and mannitol, was used. All AAB strains differed in their ethanol and lactic acid oxidation kinetics, whereby only A. pasteurianus 386B performed a fast oxidation of ethanol and lactic acid into acetic acid and acetoin, respectively. Only A. pasteurianus 386B and A. ghanensis LMG 23848(T) oxidized mannitol into fructose. Coculture fermentations with A. pasteurianus 386B or A. ghanensis LMG 23848(T) and Lactobacillus fermentum 222 in CPSM for lactic acid bacteria (LAB) containing glucose, fructose, and citric acid revealed oxidation of lactic acid produced by the LAB strain into acetic acid and acetoin that was faster in the case of A. pasteurianus 386B. A triculture fermentation with Saccharomyces cerevisiae H5S5K23, L. fermentum 222, and A. pasteurianus 386B, using CPSM for LAB, showed oxidation of ethanol and lactic acid produced by the yeast and LAB strain, respectively, into acetic acid and acetoin. Hence, acetic acid and acetoin are the major end metabolites of cocoa bean fermentation. All data highlight that A. pasteurianus 386B displayed beneficial functional roles to be used as a starter culture, namely, a fast oxidation of ethanol and lactic acid, and that these metabolites play a key role as substrates for A. pasteurianus in its indispensable cross-feeding interactions with yeast and LAB during cocoa bean fermentation.

The key to acetate: metabolic fluxes of acetic acid bacteria under cocoa pulp fermentation-simulating conditions.

Abstract: Acetic acid bacteria (AAB) play an important role during cocoa fermentation, as their main product, acetate, is a major driver for the development of the desired cocoa flavors. Here, we investigated the specialized metabolism of these bacteria under cocoa pulp fermentation-simulating conditions. A carefully designed combination of parallel 13C isotope labeling experiments allowed the elucidation of intracellular fluxes in the complex environment of cocoa pulp, when lactate and ethanol were included as primary substrates among undefined ingredients. We demonstrate that AAB exhibit a functionally separated metabolism during coconsumption of two-carbon and three-carbon substrates. Acetate is almost exclusively derived from ethanol, while lactate serves for the formation of acetoin and biomass building blocks. Although this is suboptimal for cellular energetics, this allows maximized growth and conversion rates. The functional separation results from a lack of phosphoenolpyruvate carboxykinase and malic enzymes, typically present in bacteria to interconnect metabolism. In fact, gluconeogenesis is driven by pyruvate phosphate dikinase. Consequently, a balanced ratio of lactate and ethanol is important for the optimum performance of AAB. As lactate and ethanol are individually supplied by lactic acid bacteria and yeasts during the initial phase of cocoa fermentation, respectively, this underlines the importance of a well-balanced microbial consortium for a successful fermentation process. Indeed, AAB performed the best and produced the largest amounts of acetate in mixed culture experiments when lactic acid bacteria and yeasts were both present.

Catalytic steam reforming of acetic acid as a model compound of bio-oil

Abstract: The effect of Ni catalysts promoted with Mg on catalytic activity and carbon deposition was investigated in acetic acid steam reforming. Acetic acid was chosen as representative compound for the steam reforming of bio-oil derived from biomass pyrolysis. In this study, nickel catalysts modified with Mg have been prepared by sequential impregnation method with 15 wt.% Ni and variable loadings of Mg (1–10 wt.%). The samples were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), high resolution transmission electron microscopy (HRTEM), specific surface area (BET) and temperature programmed reduction (TPR-H 2 ). Steam reforming of acetic acid was conducted in a fixed bed reactor at a temperature of 500 °C and 600 °C. Under reactive conditions, the 15Ni5Mg/Al catalyst proved to be superior to the other catalysts at 600 °C at which it presented an effluent gaseous mixture with the highest H 2 selectivity and reasonable low coke formation.

A comparative study on catalytic properties of solid acid catalysts for glycerol acetylation at low temperatures

Abstract: The catalytic properties of various types of solid acids, including silica–alumina, HUSY, dodecamolybdophosphoric acids supported on Nb2O5 (HPMo/Nb2O5) and mesoporous SBA-15 (HPMo/SBA-15), Amberlyst-15, sulfated ceria–zirconia (SCZ), propylsulfonic acid functionalized SBA-15 (PrSO3H-SBA-15), and sulfonic acid functionalized SBA-15 (SO3H-SBA-15) and microcrystalline cellulose (SO3H-Cell) catalysts, are studied for glycerol acetylation with acetic acid at low temperatures Compared at the same acidity loading and similar glycerol conversion level (∼30%) below the equilibrium, the glycerol conversion turnover rate toward di- and triacetin is considerably higher on PrSO3H-SBA-15 and Amberlyst-15, with the rates shown in order as follows: PrSO3H-SBA-15 > Amberlyst-15 > HPMo/Nb2O5 ≥ HPMo/SBA-15 > HUSY > SCZ > SiO2–Al2O3 The catalytic properties of these solid acids are relatively stable under consecutive batch runs at 353 K, whereas SO3H-SBA-15 and SO3H-Cell deactivate with a significant acidity loss due to hydrolysis of the grafted sulfonic acid groups When similar type of the solid acids is compared, the acid strength affect the rate and selectivity, favoring a higher acid strength for the facilitation of the reactions (PrSO3H-SBA-15 > Amberlyst-15; HUSY > SiO2-Al2O3; HPMo/Nb2O5 ≥ HPMo/SBA-15) However, the proportional correlation between the acid strength and the glycerol conversion turnover rate does not hold when different types of solid acids are compared The orders of magnitude higher glycerol conversion turnover rates with moderate Bronsted acid strength on the sulfonic acid functionalized catalysts suggest that the configuration of surface acid moieties attribute substantially to their catalytic activity for the reactions The acid strength on SCZ is the highest, reflecting the super acidic nature of the sites formed on the sulfated metal oxide surface, but its catalytic activity for the reactions is inferior The glycerol conversion turnover rates on the catalysts follow the Arrhenius type temperature dependence, and the characterization results indicate that the internal mass transfer resistance does not limit the reactions

Gas chromatography‑mass spectroscopy analysis of bioactive petalostigma extracts: Toxicity, antibacterial and antiviral activities

Abstract: Background: Petalostigma pubescens and Petalostigma triloculare were common components of pharmacopeia's of multiple Australian Aboriginal tribal groupings which traditionally inhabited the areas in which they grow. Among these groups, they had a myriad of medicinal uses in treating a wide variety of bacterial, fungal and viral infections. This study was undertaken to test P. pubescens and P. triloculare leaf and fruit extracts for the ability to inhibit bacterial and viral growth and thus validate Australian Aboriginal usage of these plants in treating bacterial and fungal diseases. Materials and Methods: P. pubescens, and P. triloculare leaves and fruit were extracted and tested for antimicrobial, antiviral activity and toxicity. The bioactive extracts were further examined by RP-HPLC and GC-MS to identify the component compounds. Results: The methanol, water and ethyl acetate leaf and fruit extracts of displayed potent antibacterial activity. The methanol and ethyl acetate extracts displayed the broadest specificity, inhibiting the growth of 10 of the 14 bacteria tested (71%) for the leaf extract and 9 of the 14 bacteria tested (64%) for the fruit extracts. The water extracts also had broad spectrum antibacterial activity, inhibiting the growth of 8 (57%) and 7 (50%) of the 14 bacteria tested, respectively. All antibacterial extracts were approximately equally effective against Gram-positive and Gram-negative bacteria, inhibiting the growth of 50-75% of the bacteria tested. The methanol, water and ethyl acetate extracts also displayed antiviral activity in the MS2 plaque reduction assay. The methanol and water extracts inhibited 26.6-49.0% and 85.4-97.2% of MS2 plaque formation, respectively, with the fruit extracts being more potent inhibitors. All ethyl acetate extracts inhibited 100% of MS2 plaque formation. All extracts were also non-toxic or of low toxicity. Analysis of these extracts by RP-HPLC showed that the P. triloculare ethyl acetate fruit extract was the least complex of the bioactive extracts. Subsequent analysis of this extract by GC-MS revealed that it contained 9 main compounds: acetic acid; 2,2-dimethoxybutane; 4-methyl-1,3-dioxane; decane; unadecane; 2-furanmethanol; 1,2-benzenediol; 1,2,3-benzenetriol; and benzoic acid. Conclusion: These studies validate Australian Aboriginal therapeutic usage of Petalostigma species and indicate their medicinal potential.

Effects of acid treatments on bamboo cellulose nanocrystals

Abstract: The production of nanocellulose with controlled structure from plant sources with easy availability and good sustainability is very important in science and engineering. In this work, the isolation of cellulose from bamboo and the effects of the hydrolysis of different acids on the morphology, structure, and properties of the resultant cellulose and cellulose nanocrystals were investigated. Bamboo cellulose (PHC) was first isolated from raw bamboo powder by alkali and consecutive bleaching treatments. Cellulose crystallites were then prepared by the controlled hydrolysis of PHC in acid solutions. The samples were characterized by using thermogravimetric analysis, Fourier transform infrared spectroscopy, powder X-ray diffraction, laser particle size analyzer, Scanning electron microscopy, and Transmission electron microscopy. Cellulose nanocrystals prepared from the hydrolysis of the isolated bamboo cellulose in the sulfate acid, hydrochloric acid, phosphoric acid, or acetic acid solution had the length of 3-200nm, 20-85nm, 20-40nm, and 6.5-20nm, respectively. Nanocrystals made by the uses of sulfuric acid and phosphoric acid possessed higher crystallinity and lower thermal stability than those by the uses of hydrochloric acid and a mixture of acetic acid and nitric acid. Results suggested the type of acids significantly influenced the structure, morphology, and thermal stability of cellulose crystallites. The anions in the acid solution also contributed to those differences because they affected the swelling of cellulose chains and breakage of hydrogen bonds in cellulose. The findings indicate that a judicious choice of pretreatment of the cellulose and its moieties can be used for the production of different cellulose nanocrystals.

Application of molecular imprinted polymer nanoparticles as a selective solid phase extraction for preconcentration and trace determination of 2,4-dichlorophenoxyacetic acid in the human urine and different water samples

Abstract: A molecular-imprinted polymer nanoparticles (MIP-NP) for the selective preconcentration of 2,4-dichlorophenoxyacetic acid (2,4-D) is described. It was obtained by precipitation polymerization from methacrylic acid (the functional monomer), ethylene glycol dimethacrylate (the cross-linker), 2,2′-azobisisobutyronitrile (the initiator) and 2,4-D (the template molecule) in acetonitrile solution. The MIP-NPs were characterized by thermogravimetric analysis, and by scanning electron microscopy. Imprinted 2,4-D molecules were removed from the polymeric structure using acetic acid in methanol (15:85 v/v %) as the eluting solvent. The sorption and desorption process occur within 10 min and 15 min, respectively. The maximum sorbent capacity of the molecular imprinted polymer is 89.2 mg g �1 . The relative standard deviation and limit of detection for water samples by introduced selective solid phase extraction were 4.2% and 1.25 μ gL �1 , and these data for urine samples were 4.7% and 1.80 μ gL �1 , respectively. The method was applied to the determination of 2,4-D in the urine and different water samples.