Showing papers on "Acetic acid published in 2000"

Process for producing ethanol

Abstract: A process for producing ethanol including a combination of biochemical and synthetic conversions results in high yield ethanol production with concurrent production of high value coproducts. An acetic acid intermediate is produced from carbohydrates, such as corn, using enzymatic milling and fermentation steps, followed by conversion of the acetic acid into ethanol using esterification and hydrogenation reactions. Coproducts can include corn oil, and high protein animal feed containing the biomass produced in the fermentation.

Reaction Kinetics and Chemical Equilibrium of Homogeneously and Heterogeneously Catalyzed Acetic Acid Esterification with Methanol and Methyl Acetate Hydrolysis

Abstract: The reaction kinetics and chemical equilibrium of the reversible esterification of methanol with acetic acid were investigated. This system is of major importance as a model reaction for reactive distillation. The reaction has been catalyzed both homogeneously by acetic acid itself and heterogeneously by an acidic ion-exchange resin (Amberlyst 15). The chemical equilibrium composition was measured for various temperatures and starting compositions of the reactants and products. Kinetic information was obtained at temperatures between 303.15 and 343.15 K at various starting compositions covering concentration ranges from the stoichiometric regime to the dilute regions. Both the esterification and the hydrolysis reaction were investigated to yield a model which is applicable for any starting composition. The homogeneous reaction has been described with a simple power-law model. The use of activities in the kinetic model instead of mole fractions results in a much smaller residual error. To compare pseudohom...

Diffusion of acetic and propionic acids from chitosan-based antimicrobial packaging films.

Abstract: The diffusion of acetic or propionic acids from thin (44 to 54 m m) chitosan-based antimicrobial packagingfilms in which they were incorporated was measured after immersion of the films in water, and the effects of pH (5.7,6.4, or 7.0) and temperature (4 °C, 10 °C, or 24 °C) on diffusion were investigated. The kinetics of acetic- and propi-onic-acid release deviated from the Fickian model of diffusion. Diffusion was found to be unaffected by pH in therange of values tested, but a decrease in temperature from 24 °C to 4 °C resulted in a reduction of diffusion coefficientsfrom 2.59 × 10 -12 m 2 .s -1 to 1.19 × 10 -12 m .s for acetic acid and from 1.87 × 10 m 2 .s -1 to 0.91 × 10 -12 m 2 .s -1 for propionicacid. The effect of temperature on diffusion was well (r 2 . 0.9785) described by an Arrhenius-type model with activa-tion energies of 27.19 J.mole -1 (acetic) and 24.27 J.mole (propionic). Incorporation of lauric acid or essential oils(cinnamaldehyde or eugenol) into the chitosan film at the time of preparation produced a subsequent reduction in thediffusion of acetic or propionic acid, and maximum effects were obtained with lauric acid and cinnamaldehydeincorporated to final concentrations of 1.0% and 0.5% (w/w), respectively.Key Words: diffusion, acetic, propionic, chitosan, packaging

Methanol plant retrofit for acetic acid manufacture

Abstract: The retrofitting of an existing methanol or methanol/ammonia plant to make acetic acid is disclosed. The existing plant has a reformer to which natural gas or another hydrocarbon and steam (water) are fed. Syngas is formed in the reformer. All or part of the syngas is processed to separate out carbon dioxide, carbon monoxide and hydrogen, and the separated carbon dioxide is fed either to the existing methanol synthesis loop for methanol synthesis, or back into the feed to the reformer to enhance carbon monoxide formation in the syngas. Any remaining syngas not fed to the carbon dioxide separator can be converted to methanol in the existing methanol synthesis loop along with carbon dioxide from the separator and/or imported carbon dioxide, and hydrogen from the separator. The separated carbon monoxide is then reacted with the methanol to produce acetic acid or an acetic acid precursor by a conventional process. Also disclosed is the reaction of separated hydrogen with nitrogen, in a conventional manner, to produce ammonia. Also disclosed is the reaction of a portion of the acetic acid in a conventional manner with oxygen and ethylene to form vinyl acetate monomer. The nitrogen for the added ammonia capacity in a retrofit of an original methanol plant comprising an ammonia synthesis loop, and the oxygen for the vinyl acetate monomer process, are obtained from a new air separation unit.

Asaia bogorensis gen. nov., sp. nov., an unusual acetic acid bacterium in the alpha-Proteobacteria.

Abstract: Eight Gram-negative, aerobic, rod-shaped and peritrichously flagellated strains were isolated from flowers of the orchid tree (Bauhinia purpurea) and of plumbago (Plumbago auriculata), and from fermented glutinous rice, all collected in Indonesia. The enrichment culture approach for acetic acid bacteria was employed, involving use of sorbitol medium at pH 3.5. All isolates grew well at pH 3.0 and 30 degrees C. They did not oxidize ethanol to acetic acid except for one strain that oxidized ethanol weakly, and 0.35% acetic acid inhibited their growth completely. However, they oxidized acetate and lactate to carbon dioxide and water. The isolates grew well on mannitol agar and on glutamate agar, and assimilated ammonium sulfate for growth on vitamin-free glucose medium. The isolates produced acid from D-glucose, D-fructose, L-sorbose, dulcitol and glycerol. The quinone system was Q-10. DNA base composition ranged from 59.3 to 61.0 mol% G + C. Studies of DNA relatedness showed that the isolates constitute a single species. Phylogenetic analysis based on their 16S rRNA gene sequences indicated that the isolates are located in the acetic acid bacteria lineage, but distant from the genera Acetobacter, Gluconobacter, Acidomonas and Gluconacetobacter. On the basis of the above characteristics, the name Asaia bogorensis gen. nov., sp. nov. is proposed for these isolates. The type strain is isolate 71T (= NRIC 0311T = JCM 10569T).

Engineering of the Pyruvate Dehydrogenase Bypass in Saccharomyces cerevisiae: Role of the Cytosolic Mg2+ and Mitochondrial K+ Acetaldehyde Dehydrogenases Ald6p and Ald4p in Acetate Formation during Alcoholic Fermentation

Abstract: Acetic acid plays a crucial role in the organoleptic balance of many fermented products. We have investigated the factors controlling the production of acetate by Saccharomyces cerevisiae during alcoholic fermentation by metabolic engineering of the enzymatic steps involved in its formation and its utilization. The impact of reduced pyruvate decarboxylase (PDC), limited acetaldehyde dehydrogenase (ACDH), or increased acetoacetyl coenzyme A synthetase (ACS) levels in a strain derived from a wine yeast strain was studied during alcoholic fermentation. In the strain with the PDC1 gene deleted exhibiting 25% of the PDC activity of the wild type, no significant differences were observed in the acetate yield or in the amounts of secondary metabolites formed. A strain overexpressing ACS2 and displaying a four- to sevenfold increase in ACS activity did not produce reduced acetate levels. In contrast, strains with one or two disrupted copies of ALD6 , encoding the cytosolic Mg 2+ -activated NADP-dependent ACDH and exhibiting 60 and 30% of wild-type ACDH activity, showed a substantial decrease in acetate yield (the acetate production was 75 and 40% of wild-type production, respectively). This decrease was associated with a rerouting of carbon flux towards the formation of glycerol, succinate, and butanediol. The deletion of ALD4 , encoding the mitochondrial K + -activated NAD(P)-linked ACDH, had no effect on the amount of acetate formed. In contrast, a strain lacking both Ald6p and Ald4p exhibited a long delay in growth and acetate production, suggesting that Ald4p can partially replace the Ald6p isoform. Moreover, the ald6 ald4 double mutant was still able to ferment large amounts of sugar and to produce acetate, suggesting the contribution of another member(s) of the ALD family.

Critical factors in chitin production by fermentation of shrimp biowaste

Abstract: Factors affecting Lactobacillus fermentation of shrimp waste for chitin and protein liquor production were determined. The objective of the fermentation is medium conditioning by Lactobacillus through production of proteases and lowering of the pH. The efficiency was tested by conducting fermentation of biowaste in 1-1 beakers with or without pH adjustment using different acids. Addition of 5% glucose to the biowaste supported the growth of lactic acid bacteria and led to better fermentation. Among four acids tested to control pH at the start and during fermentation, acetic acid and citric acid proved to be the most effective. In biowaste fermented with 6.7% L. plantarum inoculum, 5% glucose, and pH 6.0 adjusted with acetic acid, 75% deproteination and 86% demineralization was achieved. Replacement of acetic acid by citric acid gave 88% deproteination and 90% demineralization. The fermentation carried out in the presence of acetic acid resulted in a protein fraction that smelled good and a clean chitin fraction.

Propionic acid fermentation of glycerol and glucose by Propionibacterium acidipropionici and Propionibacterium freudenreichii ssp. shermanii.

Abstract: A comparative study was carried out in anaerobic batch cultures on 20 g/l of either glycerol or glucose using two propionibacteria strains, Propionibacterium acidipropionici and Propionibacterium freudenreichii ssp. shermanii. In all cases, fermentation end-products were the same and consisted of propionic acid as the major product, acetic acid as the main by-product and two minor metabolites, n-propanol and succinic acid. Evidence was provided that greater production of propionic acid by propionibacteria was obtained with glycerol as carbon and energy sources. P. acidipropionici showed higher efficiency in glycerol conversion to propionic acid with a faster substrate consumption (0.64 g l−1 h−1) and a higher propionic acid production (0.42 g l−1 h−1 and 0.79 mol/mol). The almost exclusive production of propionic acid from glycerol by this bacterium suggested an homopropionic tendency of this fermentation. Acetic acid final concentration was two times lower on glycerol (2 g/l) than on glucose (4 g/l) for both micro-organisms. P. freudenreichii ssp. shermanii exhibited a glycerol fermentation pattern typical of non-associated glycerol-consumption-product formation. This could indicate a particular metabolism for P. freudenreichii ssp. shermanii oriented towards the production of other specific components. These results tend to show that glycerol could be an excellent alternative to conventional carbon sources such as carbohydrates for propionic acid production.

Selective oxidation of light alkanes over hydrothermally synthesized Mo-V-M-O (M=Al, Ga, Bi, Sb, and Te) oxide catalysts

Abstract: Selective oxidations of ethane to ethene and acetic acid and of propane to acrylic acid were carried out over hydrothermally synthesized Mo-V-M-O (M=Al, Ga, Bi, Sb, and Te) complex metal oxide catalysts. All the synthesized solids were rod-shaped crystallites and gave a common XRD peak corresponding to 4.0 A d -spacing. From the different XRD patterns at low angle region below 10° and from the different shape of the cross-section of the rod crystal obtained by SEM, the solids were classified into two groups: Mo-V-M-O (M=Al, possibly Ga and Bi) and Mo-V-M-O (M=Sb, and Te). The former catalyst was moderately active for the ethane oxidation to ethene and to acetic acid. On the other hand the latter was found to be extremely active for the oxidative dehydrogenation. The Mo-V-M-O (M=Sb, and Te) catalysts were also active for the propane oxidation to acrylic acid. It was found that the grinding of the catalysts after heat-treatment at 600°C in N 2 increased the conversions of propane and enhanced the selectivity to acrylic acid. Structural arrangement of the catalytic functional components on the surface of the cross-section of the rod-shaped catalysts seems to be important for the oxidation activity and selectivity.

A method of producing ethyl acetate and an equipment for carrying out this method

Abstract: The invention relates to a method of producing ethyl acetate by reaction of ethyl alcohol with acetic acid and/or acetic anhydride in presence of a solid acidic catalyst and during simultaneous distillatory separation of reaction components, in which acetic acid or acetic anhydride or their mixture and ethyl alcohol are introduced separately in molar ratio 2:1 to 1:2.5 and in a defined quantity, based on volume unit of catalyst, into the system separated into three zones, whereby, in the reaction zone, the reaction runs simultaneously with the distillatory separation of components, acetic acid feed is introduced into the reaction zone or above the zone and ethyl alcohol feed is introduced into the reaction zone or below this zone, in the upper separation zone, the volatile mixture is separated, thereafter, it is cooled to 5 to 70 °C and then separated to water and organic phases and this organic phase with high ethyl acetate content is drawn off and partially returned as reflux flow into this system, whereby, the ratio of the input components feed and the organic phase reflux flow is 1:1 to 1:20. A subject matter of this invention is also an equipment for carrying out this method.

Effects of Acid Adaptation of Escherichia coli O157:H7 on Efficacy of Acetic Acid Spray Washes To Decontaminate Beef Carcass Tissue

Abstract: Exposure to low pH and organic acids in the bovine gastrointestinal tract may result in the induced acid resistance of Escherichia coli O157:H7 and other pathogens that may subsequently contaminate beef carcasses. The effect of acid adaptation of E. coli O157:H7 on the ability of acetic acid spray washing to reduce populations of this organism on beef carcass tissue was examined. Stationary-phase acid resistance and the ability to induce acid tolerance were determined for a collection of E. coli O157:H7 strains by testing the survival of acid-adapted and unadapted cells in HCl-acidified tryptic soy broth (pH 2.5). Three E. coli O157:H7 strains that were categorized as acid resistant (ATCC 43895) or acid sensitive (ATCC 43890) or that demonstrated inducible acid tolerance (ATCC 43889) were used in spray wash studies. Prerigor beef carcass surface tissue was inoculated with bovine feces containing either acid-adapted or unadapted E. coli O157:H7. The beef tissue was subjected to spray washing treatments with water or 2% acetic acid or left untreated. For strains ATCC 43895 and 43889, larger populations of acid-adapted cells than of unadapted cells remained on beef tissue following 2% acetic acid treatments and these differences remained throughout 14 days of 4°C storage. For both strains, numbers of acid-adapted cells remaining on tissue following 2% acetic acid treatments were similar to numbers of both acid-adapted and unadapted cells remaining on tissue following water treatments. For strain ATCC 43890, there was no difference between populations of acid-adapted and unadapted cells remaining on beef tissue immediately following 2% acetic acid treatments. These data indicate that adaptation to acidic conditions by E. coli O157:H7 can negatively influence the effectiveness of 2% acetic acid spray washing in reducing the numbers of this organism on carcasses.

Kinetics of Catalytic Esterification of Acetic Acid and Amyl Alcohol over Dowex

Abstract: The kinetic behavior of the heterogeneous esterification of acetic acid with amyl alcohol over an acidic cation-exchange resin, Dowex 50Wx8-100, was investigated. The experiments were conducted in a fixed-bed reactor at temperatures from 323 to 393 K and at molar ratios of feed (amyl alcohol to acetic acid) from 1 to 10. The equilibrium conversion of acetic acid was found to increase with increasing reaction temperature. A water-rich phase (the second liquid phase) appeared in the reacting mixture when the feed composition was close to stoichiometric. Gas bubble formation was observed when the reaction temperature was as high as 393 K. The kinetic data were correlated with the quasi-homogeneous, Langmuir−Hinshelwood, Eley−Rideal, and modified Langmuir−Hinshelwood models. The modified Langmuir-Hinshelwood model yielded the best representation for the kinetic behavior of the reaction over wide ranges of temperature and feed composition.

Influence of phenolic compounds on the physiology of Œnococcus œni from wine

Abstract: This study shows that the growth of Œnococcus œni CECT 4100 in a synthetic medium is affected by phenolic compounds in different ways, depending on their type and concentration. Generally they have no effects at low concentrations, but hydroxycinnamic acids are inhibitory at high concentrations. Malolactic fermentation was stimulated in the presence of catechin and quercetin, but increasingly delayed with increasing amounts of p-coumaric acid. Gallic acid appeared to delay or inhibit the formation of acetic acid from citric acid. This could lead to a better control of malolactic fermentation and suppress the increase in volatile acidity, which is undesirable in the wine-making process.

Energetics of the effect of acetic acid on growth of Saccharomyces cerevisiae.

Abstract: In batch cultures of a respiratory deficient mutant of Saccharomyces cerevisiae the maximum specific growth rate and the yield coefficient decreased, but the specific glucose consumption rate increased, in the presence of acetic acid. The ATP yield decreased from approximately 14 to 4 g biomass (mol ATP)−1 when the concentration of acetic acid increased from 0 to 170 mM. Intracellular acidification was much weaker than previously reported for non-adapted cells. A linear relation was obtained between the ATP specific production rate and the uptake rate of acetic acid, suggesting that about 1 mol ATP is consumed per mol of acetic acid diffusing into the cells.

Acetic Acid Suppresses the Increase in Disaccharidase Activity That Occurs during Culture of Caco-2 Cells

Abstract: To understand how blood glucose level is lowered by oral administration of vinegar, we examined effects of acetic acid on glucose transport and disaccharidase activity in Caco-2 cells. Cells were cultured for 15 d in a medium containing 5 mmol/L of acetic acid. This chronic treatment did not affect cell growth or viability, and furthermore, apoptotic cell death was not observed. Glucose transport, evaluated with a nonmetabolizable substrate, 3-O-methyl glucose, also was not affected. However, the increase of sucrase activity observed in control cells (no acetic acid) was significantly suppressed by acetic acid (P < 0.01). Acetic acid suppressed sucrase activity in concentration- and time-dependent manners. Similar treatments (5 mmol/L and 15 d) with other organic acids such as citric, succinic, L-maric, L-lactic, L-tartaric and itaconic acids, did not suppress the increase in sucrase activity. Acetic acid treatment (5 mmol/L and 15 d) significantly decreased the activities of disaccharidases (sucrase, maltase, trehalase and lactase) and angiotensin-I-converting enzyme, whereas the activities of other hydrolases (alkaline phosphatase, aminopeptidase-N, dipeptidylpeptidase-IV and gamma-glutamyltranspeptidase) were not affected. To understand mechanisms underlying the suppression of disaccharidase activity by acetic acid, Northern and Western analyses of the sucrase-isomaltase complex were performed. Acetic acid did not affect the de novo synthesis of this complex at either the transcriptional or translational levels. The antihyperglycemic effect of acetic acid may be partially due to the suppression of disaccharidase activity. This suppression seems to occur during the post-translational processing.

Potent Aroma Compounds of Two Red Wine Vinegars

Abstract: Gas chromatography olfactometry (GCO) was used to determine key aroma compounds of two red wine vinegars. Sensory analysis was performed to choose the best neutralization agent of acetic acid (NaOH or MgO) and to test representativeness of four extracts obtained by different methods (dichloromethane extraction, XAD-2, mixture of XAD-2 and XAD-7, and Extrelut resins extraction). Neutralization with NaOH followed by dichloromethane extraction was selected to extract volatile compounds of vinegars. Key odorant compounds were determined by GCO based on detection frequency with 13 people. In the two red wine vinegars, 13 odors were perceived by at least 70% of the panelists, and 8 compounds among the 13 were identified: acetic acid, 3-methylbutyric acid, 2-phenyl-1-ethanol, 2,3-butanedione, butyric acid, 2-methylbutyric acid, mixture of 2- and 3-methyl-1-butanol, and two newly identified compounds in vinegar, 3-hydroxy-2-pentanone and 3-(methylthio)-1-propanal. Quantification of all the volatile compounds was...

Wood Hydrolysis and Hydrolyzate Detoxification for Subsequent Xylitol Production

Abstract: This study deals with two different aspects of the transformation of lignocellulosics into xylitol: the optimization of conditions for wood hydrolysis and the setting-up of an adequate hydrolyzate detoxification procedure necessary to obtain high xylitol yields in the successive fermentation process. A comparison between the processes of wood autohydrolysis (steam explosion) and pre-hydrolysis with dilute sulfuric acid, carried out batch-wise in laboratory scale, shows comparable yields, either in terms of final concentrations of xylose and pentose sugars in the hydrolyzate or of solubilised fraction of wood. On the other hand, notwithstanding the longer time required, the pre-hydrolysis with dilute sulfuric acid produced acid hydrolyzates with lower contents of inhibiting substances (furfural, acetic acid, etc.). In order to obtain satisfactory xylitol yields from the hydrolysate produced by steam explosion, samples of this hydrolyzate were submitted to different detoxification techniques and then fermented batch-wise by a Pachysolen tannophilus strain previously adapted to this substrate. The best detoxification was performed by adding to the traditional overliming with Ca(OH)2 and sulfite reduction, three steps of a) filtration to remove insoluble substances, b) stripping of acetic acid and furfural, and c) lignin-derived compounds removal by adsorption on charcoal. The fermentation of this hydrolyzate was very effective, achieving a final xylitol concentration of 39.5 g/l from 89.0 g/l xylose after 96 h, corresponding to a volumetric productivity of 0.41 g/lh and a product yield of 0.63 g/g.