Showing papers on "Acetic acid published in 1998"

Expression of Clostridium acetobutylicum ATCC 824 Genes in Escherichia coli for Acetone Production and Acetate Detoxification

Abstract: A synthetic acetone operon (ace4) composed of four Clostridium acetobutylicum ATCC 824 genes (adc, ctfAB, and thl, coding for the acetoacetate decarboxylase, coenzyme A transferase, and thiolase, respectively) under the control of the thl promoter was constructed and was introduced into Escherichia coli on vector pACT. Acetone production demonstrated that ace4 is expressed in E. coli and resulted in the reduction of acetic acid levels in the fermentation broth. Since different E. coli strains vary significantly in their growth characteristics and acetate metabolism, ace4 was expressed in three E. coli strains: ER2275, ATCC 11303, and MC1060. Shake flask cultures of MC1060(pACT) produced ca. 2 mM acetone, while both strains ER2275(pACT) and ATCC 11303(pACT) produced ca. 40 mM acetone. Glucose-fed cultures of strain ATCC 11303(pACT) resulted in a 150% increase in acetone titers compared to those of batch shake flask cultures. External addition of sodium acetate to glucose-fed cultures of ATCC 11303(pACT) resulted in further increased acetone titers. In bioreactor studies, acidic conditions (pH 5.5 versus 6.5) improved acetone production. Despite the substantial acetone evaporation due to aeration and agitation in the bioreactor, 125 to 154 mM acetone accumulated in ATCC 11303(pACT) fermentations. These acetone titers are equal to or higher than those produced by wild-type C. acetobutylicum. This is the first study to demonstrate the ability to use clostridial genes in nonclostridial hosts for solvent production. In addition, acetone-producing E. coli strains may be useful hosts for recombinant protein production in that detrimental acetate accumulation can be avoided.

A Nine-Zone Simulating Moving Bed for the Recovery of Glucose and Xylose from Biomass Hydrolyzate

Abstract: A nine-zone simulated moving bed (SMB) process was developed to recover two sugars, glucose and xylose, from biomass hydrolyzate with 88% recovery and near 100% purity. The SMB system consists of two coupled binary SMB rings which are operated at the same switching time. The first ring consists of five zones, in which sulfuric acid (a fast-moving solute) is recovered as the raffinate product, acetic acid (a slow-moving solute) is partially recovered as the extract product, and a mixture of the two sugars (intermediate solute) and the rest of the acetic acid is recovered in a bypass stream, which is input as the feed to the second ring. The second ring consists of four zones, in which the sugars are recovered as the raffinate product and acetic acid is recovered as the extract product. Experimental SMB data obtained using either hydrolyzate or synthetic mixtures of glucose, xylose, sulfuric acid, and acetic acid are presented and analyzed with a lumped mass-transfer model. Single-component and multicompone...

A Novel Fermentation Pathway in an Escherichia coli Mutant Producing Succinic Acid, Acetic Acid, and Ethanol

Abstract: Escherichia coli strain NZN111, which is unable to grow fermentatively because of insertional inactivation of the genes encoding pyruvate: formate lyase and the fermentative lactate dehydrogenase, gave rise spontaneously to a chromosomal mutation that restored its ability to ferment glucose. The mutant strain, named AFP111, fermented glucose more slowly than did its wild-type ancestor, strain W1485, and generated a very different spectrum of products. AFP111 produced succinic acid, acetic acid, and ethanol in proportions of approx 2:1:1. Calculations of carbon and electron balances accounted fully for the observed products; 1 mol of glucose was converted to 1 mol of succinic acid and 0.5 mol each of acetic acid and ethanol. The data support the emergence in E. coli of a novel succinic acid:acetic acid:ethanol fermentation pathway.

The DFRC Method for Lignin Analysis. 6. A Simple Modification for Identifying Natural Acetates on Lignins

Abstract: By modifying the derivatization followed by reductive cleavage (DFRC) procedure to be completely acetate-free, the presence and regiochemistry of natural acetates on lignins can be determined. Derivatization is conducted with propionyl bromide in propionic acid instead of acetyl bromide in acetic acid; reductive cleavage uses zinc in propionic acid instead of in acetic acid, and the final derivatization step uses propionic anhydride instead of acetic anhydride. Applying the modified procedure to lignins or cell walls from kenaf bast fibers proved that their lignins are highly γ-acetylated, mainly on syringyl units, supporting results of previous NMR work. Application to isolated hardwood lignins or cell walls confirmed reported low-level acetylation and elucidated its γ-regiochemistry. The DFRC method therefore provides a convenient screen for many types of lignin acylation. Keywords: Lignin; acylation; acetylation; DFRC; lignin acetates; lignin esters; kenaf; Tainung kenaf; aspen

Enantiodifferentiation in asymmetric sonochemical hydrogenations

Abstract: The effect of sonochemical pretreatment on the enantioselectivity of Pt/Al2O3–cinchonidine-catalyzed ethyl pyruvate hydrogenation was studied at different hydrogen pressures in various solvents, mainly in acetic acid. The sonochemical pretreatment of a commercial Pt/Al2O3–cinchonidine catalytic system in acetic acid resulted in enhanced enantioselectivity providing excellent ee values (97% ee) under mild and widely varied experimental conditions. Moreover, the application of ultrasonics provides a possibility of the catalyst recycling without regeneration. The catalyst was tested by transmission electron microscopy to determine the effect of the sonication on the metal particle size morphology.

Acetate production from whey lactose using co-immobilized cells of homolactic and homoacetic bacteria in a fibrous-bed bioreactor

Abstract: Acetate was produced from whey lactose in batch and fed-batch fermentations using co-immobilized cells of Clostridium formicoaceticum and Lactococcus lactis. The cells were immobilized in a spirally wound fibrous sheet packed in a 0.45-L column reactor, with liquid circulated through a 5-L stirred-tank fermentor. Industrial-grade nitrogen sources, including corn steep liquor, casein hydrolysate, and yeast hydrolysate, were studied as inexpensive nutrient supplements to whey permeate and acid whey. Supplementation with either 2.5% (v/v) corn steep liquor or 1.5 g/L casein hydrolysate was adequate for the cocultured fermentation. The overall acetic acid yield from lactose was 0.9 g/g, and the productivity was 0.25 g/(L h). Both lactate and acetate at high concentrations inhibited the homoacetic fermentation. To overcome these inhibitions, fed-batch fermentations were used to keep lactate concentration low and to adapt cells to high-concentration acetate. The final acetate concentration obtained in the fed-batch fermentation was 75 g/L, which was the highest acetate concentration ever produced by C. formicoaceticum. Even at this high acetate concentration, the overall productivity was 0.18 g/(L h) based on the total medium volume and 1.23 g/(L h) based on the fibrous-bed reactor volume. The cells isolated from the fibrous-bed bioreactor at the end of this study were more tolerant to acetic acid than the original culture used to seed the bioreactor, indicating that adaptation and natural selection of acetate-tolerant strains occurred. This cocultured fermentation process could be used to produce a low-cost acetate deicer from whey permeate and acid whey.

Ester co-production

Abstract: This invention relates to a process for the simultaneous co-production of ethyl acetate and n-butyl acetate, in a reaction of a mixture of ethanol and n-butanol with acetic acid in the liquid phase in the presence of an acidic catalyst using a series or reactor and distillation columns so as to recover substantially pure ethyl acetate and substantially pure n-butyl acetate. The process is capable of using relatively impure reactants and provides for removing some of the aldehyde type impurities by the use of resin guard beds.

Structural Variation in Manganase Complexes: Synthesis and Characterization of Manganese Complexes from Carboxylate-containing Chelating Ligands.

Abstract: Three manganese(II) complexes, [MnII2L12(H2O)4](ClO4)2·H2O (1, L1H = (bis(2-pyridylmethyl)amino)acetic acid), [MnII2L22(H2O)2](BPh4)2·2EtOH·2H2O (2, L2H = 3-(bis(2-pyridylmethyl)amino)propionic aci...

Measurement of the Effects of Acetic Acid and Extracellular pH on Intracellular pH of Nonfermenting, Individual Saccharomyces cerevisiae Cells by Fluorescence Microscopy

Abstract: The effects of acetic acid and extracellular pH (pHex) on the intracellular pH (pHi) of nonfermenting, individual Saccharomyces cerevisiae cells were studied by using a new experimental setup comprising a fluorescence microscope and a perfusion system. S. cerevisiae cells grown in brewer’s wort to the stationary phase were stained with fluorescein diacetate and transferred to a perfusion chamber. The extracellular concentration of undissociated acetic acid at various pHex values was controlled by perfusion with 2 g of total acetic acid per liter at pHex 3.5, 4.5, 5.6, and 6.5 through the chamber by using a high-precision pump. The pHi of individual S. cerevisiae cells during perfusion was measured by fluorescence microscopy and ratio imaging. Potential artifacts, such as fading and efflux of fluorescein, could be neglected within the experimental time used. At pHex 6.5, the pHi of individual S. cerevisiae cells decreased as the extracellular concentration of undissociated acetic acid increased from 0 to 0.035 g/liter, whereas at pHex 3.5, 4.5, and 5.6, the pHi of individual S. cerevisiae cells decreased as the extracellular concentration of undissociated acetic acid increased from 0 to 0.10 g/liter. At concentrations of undissociated acetic acid of more than 0.10 g/liter, the pHi remained constant. The decreases in pHi were dependent on the pHex; i.e., the decreases in pHi at pHex 5.6 and 6.5 were significantly smaller than the decreases in pHi at pHex 3.5 and 4.5.

Method for producing acetaldehyde from acetic acid

Abstract: A method of producing acetaldehyde hydrogenates acetic acid in the presence of an iron oxide catalyst containing between 2.5 and 90 wt % Pd, more preferably 10 and 80 wt % Pd and most preferably 20 and 60 wt % Pd. The catalyst has a specific surface area of less than 150 m 2 /g. Hydrogen and acetic acid are fed to a reactor in a hydrogen to acetic acid ratio of 2:1 to 25:1, more preferably in a hydrogen to acetic acid ratio of 3:1 to 15:1 and most preferably in a hydrogen to acetic acid ratio of 4:1 to 12:1. The hydrogenation is performed at a temperature of about 250° C. to 400° C., more preferably about 270° C. to 350° C. and most preferably about 280° C. to 325° C. The hydrogenation of acetic acid produces a partially gaseous product, and acetaldehyde is absorbed from the partially gaseous product with a solvent containing acetic acid. The gas remaining after the absorption step contains hydrogen, and this gas is recycled for the hydrogenation of acetic acid. The absorbed acetaldehyde is distilled to isolate same. After acetaldehyde is isolated from unreacted acetic acid and the other products via distillation, the unreacted acetic acid is separated from the other products using azeotropic distillation. Water is contained in the other products, and the azeotrope is an azeotrope of ethyl acetate and water. The unreacted acetic acid is separated in a column, and the column is controlled to contain an ethyl acetate rich azeotrope of ethyl acetate and water.

Studies of lead corrosion in acetic acid environments

Abstract: Many lead artifacts are danzaged after being kept for a short period in enclosures that contain materials which emit carboxylic acids. The formation of corrosion products and the corrosion sensitivity of lead were studied under experimental conditions in which the duration of exposure, the acetic acid (ethanoic acid) concentration and the relative humidity (RH) were varied. At 54% RH, in the acetic acid concentration range studied, weight gain was maximun at around 4mgm−3. Over a period of 12 months, with RH levels below 75%, no damage was detected on lead samples at acetic acid concentrations below 0·43mgm−3. However, variations in the composition and morphology of lead as well as the presence of other carbonyl compounds in enclosures may affect the rate of corrosion. For these reasons, a total concentration of low molecular weight carbonyl compounds no higher than 0·1mgm−3 is recommended. Strategies to maintain the concentration of carbonyl compounds below 0·1mgm−3 are proposed.

Mechanisms underlying the transport and intracellular metabolism of acetic acid in the presence of glucose in the yeast Zygosaccharomyces bailii

Abstract: Zygosaccharomyces bailii ISA 1307 displays biphasic growth in a medium containing a mixture of glucose (0.5%, w/v) and acetic acid (0.5%, w/v), pH 5.0 and 3.0. In cells harvested during the first growth phase, no activity of a mediated acetic acid transport system was found. Incubation of these cells in phosphate buffer with cycloheximide for 1 h restored activity of an acetic acid carrier which behaved as the one present in glucose-grown cells. These results indicated that the acetic acid carrier is probably present in cells from the first growth phase of the mixed medium but its activity was affected by the presence of acetic acid in the culture medium. In glucose-grown cells, after incubation in phosphate buffer with glucose and acetic acid, the activity of the acetic acid carrier decreased significantly with increased acid concentration in the incubation buffer. At acid concentrations above 16.7 mM, no significant carrier activity was detectable. Furthermore, the intracellular acid concentration increased with the extracellular one and was inversely correlated with the activity of the acetic acid carrier, suggesting the involvement of a feedback inhibition mechanism in the regulation of the carrier. During biphasic growth, the first phase corresponded to a simultaneous consumption of glucose and acetic acid, and the second to the utilization of the remaining acid. The enzyme acetyl-CoA synthetase was active in both growth phases, even in the presence of glucose. Activity of isocitrate lyase and phosphoenolpyruvate carboxykinase was found only in acetic-acid-grown cells. Thus it appears that both membrane transport and acetyl-CoA synthetase and their regulation are important for Z. bailii to metabolize acetic acid in the presence of glucose. This fact correlates with the high resistance of this yeast to environments with mixtures of sugars and acetic acid such as those often present during wine fermentation.

Polyaniline Membranes for Pervaporation of Carboxylic Acids and Water

Abstract: Free-standing polyaniline films are studied as pervaporation membranes for separating carboxylic acid/water mixtures. Changing polyaniline membranes from an undoped to a fully doped state has a dramatic effect on their selectivity. For example, with a 52 wt % acetic acid/48 wt % water feed, the undoped, base form of polyaniline leads to only a relatively modest separation of water (68 wt % water in permeate; αH2O = 2.4), while the doped, acid form of polyaniline shows a remarkably enhanced separation ability (>99 wt % water in permeate; αH2O > 1300). The improved selectivity of doped polyaniline is due in part to the hydrophilicity induced in the polymer by the acid dopants. Fully doped polyaniline appears to restrict the permeation of carboxylic acids mainly based on their effective sizes. Whereas formic acid (solvated diameter = 3.5 A) can permeate through a doped polyaniline membrane, the larger acetic acid (4.5 A) has an exceedingly low rate of permeation, and the even larger propionic acid (5.5 A) is...