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PubMed1976

Factors affecting rate of methane formation from acetic acid by enriched methanogenic cultures.

A stable enrichment culture converting acetic acid to methane was successfully obtained from a pear waste digester, using a synthetic substrate solution with acetic acid as the main carbon source. This enrichment culture converted up to 10 mmol of acetic acid per litre per day at 35 degrees C and did not use hydrogen or formic acid in appreciable amounts as substrate for methane production instead of, or in addition to, acetic acid. The rate of conversion of acetic acid to methane was maximum at temperature of 40-45 degrees C, at a pH of 6.5 to 7.1, and was adversely affected by exposure to air, reducing agents, and high salt concentrations. The rate of conversion was independent of acetic acid concentration between 0.2 and 100 mM, but dropped markedly at concentrations below 0.2 mM.

Acetates↗
PubMed2003

Characterization, localization and functional analysis of Gpr1p, a protein affecting sensitivity to acetic acid in the yeast Yarrowia lipolytica.

Adaptation of cells to acetic acid requires a hitherto unknown number of proteins. Studies on the GPR1 gene and its encoded protein in the ascomycetous fungus Yarrowia lipolytica have revealed an involvement of this protein in the molecular processes of adaptation to acetic acid. Gpr1p belongs to a novel family of conserved proteins in prokaryotic and eukaryotic organisms that is characterized by the two motifs (A/G)NPAPLGL and SYG(X)FW (GPR1_FUN34_YaaH protein family). Analysis of four trans-dominant mutations and N-terminal deletion analysis of Gpr1p identified the amino acid sequence FGGTLN important for function of this protein in Y. lipolytica. Deletion of GPR1 slowed down adaptation to acetic acid, but had no effect on growth in the presence of acetic acid. Expression of GPR1 is induced by acetic acid and moderately repressed by glucose. It was shown by subcellular fractionation that Gpr1p is an integral membrane protein, which is also suggested by the presence of five to six putative transmembrane spanning regions. Fluorescence microscopy confirmed a localization to the plasma membrane. A model is presented describing a hypothetical function of Gpr1p during adaptation to acetic acid.

Acetic Acid↗
PubMed1992

Effect of acetic acid on xylose conversion to ethanol by genetically engineered E. coli.

Efficient utilization of the pentosan fraction of hemicellulose from lignocellulosic feedstocks offers an opportunity to increase the yield and to reduce the cost of producing fuel ethanol. During prehydrolysis (acid hydrolysis or autohydrolysis of hemicellulose), acetic acid is formed as a consequence of the deacetylation of the acetylated moiety of hemicellulose. Recombinant Escherichia coli B (ATCC 11303), carrying the plasmid pLO1297 with pyruvate decarboxylase and alcohol dehydrogenase II genes from Zymomonas mobilis (CP4), converts xylose to ethanol with a product yield that approaches theoretical maximum. Although other pentose-utilizing microorganisms are inhibited by acetic acid, the recombinant E. coli displays a high tolerance for acetic acid. In xylose fermentations with a synthetic medium (Luria broth), where the pH was controlled at 7, neither yield nor productivity was affected by the addition of 10.7 g/L acetic acid. Nutrient-supplemented, hardwood (aspen) hemicellulose hydrolysate (40.7 g/L xylose) was completely fermented to ethanol (16.3 g/L) in 98 h. When the acetic acid concentration was reduced from 5.6 to 0.8 g/L, the fermentation time decreased to 58 h. Overliming, with Ca(OH)2 to pH 10, followed by neutralization to pH 7 with sulfuric acid and removal of insolubles, resulted in a twofold increase in volumetric productivity. The maximum productivity was 0.93 g/L/h. The xylose-to-ethanol conversion efficiency and productivity in Ca(OH)2-treated hardwood prehydrolysate, fortified with only mineral salts, were 94% and 0.26 g/L/h, respectively. The recombinant E. coli exhibits a xylose-to-ethanol conversion efficiency that is superior to that of other pentose-utilizing yeasts currently being investigated for the production of fuel ethanol from lignocellulosic materials.

Acetates↗
PubMed2005

Adsorption of acetic acid on ice: experiments and molecular dynamics simulations.

Adsorption study of acetic acid on ice surfaces was performed by combining experimental and theoretical approaches. The experiments were conducted between 193 and 223 K using a coated wall flow tube coupled to a mass spectrometric detection. Under our experimental conditions, acetic acid was mainly dimerized in the gas phase. The surface coverage increases with decreasing temperature and with increasing concentrations of acetic acid dimers. The obtained experimental surface coverages were fitted according to the BET theory in order to determine the enthalpy of adsorption deltaH(ads) and the mololayer capacity N(M(dimers)) of the acetic acid dimers on ice: deltaH(ads) = (-33.5 +/- 4.2) kJ mol(-1), N(M(dimers)) = (l1.27 +/- 0.25) x 10(14) dimers cm(-2). The adsorption characteristics of acetic acid on an ideal ice I(n)(0001) surface were also studied by means of classical molecular dynamics simulations in the same temperature range. The monolayer capacity, the configurations of the molecules in their adsorption sites, and the corresponding adsorption energies have been determined for both acetic acid monomers and dimers, and compared to the corresponding data obtained from the experiments. In addition, the theoretical results show that the interaction with the ice surface could be strong enough to break the acetic acid dimers that exist in the gas phase and leads to the stabilization of acetic acid monomers on ice.

Journal Article↗
PubMed2002

Site-specific incorporation of (aminooxy)acetic acid into proteins.

By employing a general biosynthetic method for the elaboration of proteins containing unnatural amino acid analogues, we incorporated (aminooxy)acetic acid into positions 10 and 27 of Escherichia coli dihydrofolate reductase. Introduction of the modified amino acid into DHFR was accomplished in an in vitro protein biosynthesizing system by readthrough of a nonsense (UAG) codon with a suppressor tRNA that had been activated with (aminooxy)acetic acid. Incorporation of the amino acid proceeded with reasonable efficiency at codon position 10 but less well at position 27. (Aminooxy)acetic acid was also incorporated into position 72 of DNA polymerase beta. Peptides containing (aminooxy)acetic acid have been shown to adopt a preferred conformation involving an eight-membered ring that resembles a gamma-turn. Accordingly, the present study may facilitate the elaboration of proteins containing conformationally biased peptidomimetic motifs at predetermined sites. The present results further extend the examples of ribosomally mediated formation of peptide bond analogues of altered connectivity and provide a conformationally biased linkage at a predetermined site. It has also been shown that the elaborated protein can be cleaved chemically at the site containing the modified amino acid.

Amino Acid Sequence↗
PubMed2005

Boswellic acid acetate induces apoptosis through caspase-mediated pathways in myeloid leukemia cells.

The mechanism of the cytotoxic effect of boswellic acid acetate, a 1:1 mixture of alpha-boswellic acid acetate and beta-boswellic acid acetate, isolated from Boswellia carterri Birdw on myeloid leukemia cells was investigated in six human myeloid leukemia cell lines (NB4, SKNO-1, K562, U937, ML-1, and HL-60 cells). Morphologic and DNA fragmentation assays indicated that the cytotoxic effect of boswellic acid acetate was mediated by induction of apoptosis. More than 50% of the cells underwent apoptosis after treatment with 20 mug/mL boswellic acid for 24 hours. This apoptotic process was p53 independent. The levels of apoptosis-related proteins Bcl-2, Bax, and Bcl-XL were not modulated by boswellic acid acetate. Boswellic acid acetate induced Bid cleavage and decreased mitochondrial membrane potential without production of hydrogen peroxide. A general caspase inhibitor (Z-VAD-FMK) and a specific caspase-8 inhibitor II (Z-IETD-FMK) blocked boswellic acid acetate-induced apoptosis. The mRNAs of death receptors 4 and 5 (DR4 and DR5) were induced in leukemia cells undergoing apoptosis after boswellic acid acetate treatment. These data taken together suggest that boswellic acid acetate induces myeloid leukemia cell apoptosis through activation of caspase-8 by induced expression of DR4 and DR5, and that the activated caspase-8 either directly activates caspase-3 by cleavage or indirectly by cleaving Bid, which in turn decreases mitochondria membrane potential.

Amino Acid Chloromethyl Ketones↗
PubMed2005

Effect of indole-3-acetic acid derivatives on neuroepithelium in rat embryos.

Indole-3-acetic acid (IAA), a natural auxin, induces microencephaly in rats exposed to IAA during gestation days (Days) 12-14, corresponding to the early stage of cerebral cortex development. The purpose of this study was to examine the effects of 5 IAA derivatives administration in pregnant rats on neuroepithelial cells in the embryos. N-Methylindole-3-acetic acid (1Me-IAA), 2-Methylindole-3-acetic acid (2Me-IAA), 2-Methyl-5-methoxyindole-3-acetic acid (2Me-5MeO-IAA), 5-Methoxyindole-3-acetic acid (5MeO-IAA), Indole butyric acid (IBA), and IAA were administered at 1,000 mg/kg except for 2Me-IAA at 500 mg/kg on Days 12, 13 and 14, and then embryos/fetuses were harvested on Day 14.5 or 21. The dams in the 1Me-IAA and 2Me-IAA groups exhibited rigidity and a decrease in locomotor activity. Although a decrease in the absolute brain weight was observed in the 1Me-IAA, 5MeO-IAA, IBA and IAA groups, a decrease in the relative brain weight was observed in only the IAA group. Histopathologically, apoptotic cells were observed mainly in the medial and dorsal layer of the neuroepithelium in the 5MeO-IAA and IAA groups on Day 14.5. The degree of induced neuroepithelial cell apoptosis was less in the 5MeO-IAA group than in the IAA group. However, it was confirmed that the histopathological changes induced by 5MeO-IAA were quite similar to the lesions induced by IAA and may have resulted from the same mechanisms.

Administration, Oral↗
PubMed2002

The antitumour activity of 5,6-dimethylxanthenone-4-acetic acid (DMXAA) in TNF receptor-1 knockout mice.

5,6-dimethylxanthenone-4-acetic acid, a novel antivascular anticancer drug, has completed Phase I clinical trial. Its actions in mice include tumour necrosis factor induction, serotonin release, tumour blood flow inhibition, and the induction of tumour haemorrhagic necrosis and regression. We have used mice with a targeted disruption of the tumour necrosis factor receptor-1 gene as recipients for the colon 38 carcinoma to determine the role of tumour necrosis factor signalling in the action of 5,6-dimethylxanthenone-4-acetic acid. The pharmacokinetics of 5,6-dimethylxanthenone-4-acetic acid, as well as the degree of induced plasma and tissue tumour necrosis factor, were similar in tumour necrosis factor receptor-1(-/-) and wild-type mice. However, the maximum tolerated dose of 5,6-dimethylxanthenone-4-acetic acid was considerably higher in tumour necrosis factor receptor-1(-/-) mice (>100 mg kg(-1)) than in wild-type mice (27.5 mg kg(-1)). The antitumour activity of 5,6-dimethylxanthenone-4-acetic acid (25 mg kg(-1)) was strongly attenuated in tumour necrosis factor receptor-1(-/-) mice. However, the reduced toxicity in tumour necrosis factor receptor-1(-/-) mice allowed the demonstration that at a higher dose (50 mg kg(-1)), 5,6-dimethylxanthenone-4-acetic acid was curative and comparable in effect to that of a lower dose (25 mg kg(-1)) in wild-type mice. The 5,6-dimethylxanthenone-4-acetic acid -induced rise in plasma 5-hydroxyindoleacetic acid, used to reflect serotonin production in a vascular response, was larger in colon 38 tumour bearing than in non-tumour bearing tumour necrosis factor receptor-1(-/-) mice, but in each case the response was smaller than the corresponding response in wild-type mice. The results suggest an important role for tumour necrosis factor in mediating both the host toxicity and antitumour activity of 5,6-dimethylxanthenone-4-acetic acid, but also suggest that tumour necrosis factor can be replaced by other vasoactive factors in its antitumour action, an observation of relevance to current clinical studies.

Animals↗
PubMed2004

[Formation of an acetic-acid type microbial metabolism pathway and its stability during the course of sulfate-reduction].

Continuous-flow experiment was conducted in an acidogenic sulfate-reducing reactor supplied with molasses as sole carbon resource and sulfate sodium as electron acceptor. The composition of Volatile fat acid(VFA) in terminal liquid products, the distribution of acetic acid, the existence of microbial populations and the interspecific relationship between sulfate-reducing bacteria (SRB) and acidogenic bacteria (AB) were investigated in different experimental stages when sulfate removal rate and gas production maintained at a relatively stable status. The experimental results showed that an acetic-acid type microbial metabolism pathway was formed based on the fact that the proportion of acetic acid in terminal liquid products was as high as 50% to 82%. It was also explained the formation of acetic-acid type microbial metabolism pathway was resulted from acetic acid accumulation in the terminal liquid products, which was subjected to the bio-chain cooperation relationship between populations of SRB and AB, and the incomplete-oxidation of organic substance in acidogenic-phase reactor of two-phase anaerobic treatment process. It was also presented that the formation of acetic-acid type microbial metabolism pathway depended on the capability of acetic-acid utilized-SRB (ASRB) population competing against other populations and its ability of acetic acid consumption. Furthermore, this kind of metabolism pathway could offer suitable carbon resource for methane producing reactor in the two-phase anaerobic treatment process, and has significant effect on the sulfate removal rate of the whole treatment system and its running stability.

Acetic Acid↗
PubMed1999

Main and interaction effects of acetic acid, furfural, and p-hydroxybenzoic acid on growth and ethanol productivity of yeasts.

The influence of the factors acetic acid, furfural, and p-hydroxybenzoic acid on the ethanol yield (YEtOH) of Saccharomyces cerevisiae, bakers' yeast, S. cerevisiae ATCC 96581, and Candida shehatae NJ 23 was investigated using a 2(3)-full factorial design with 3 centrepoints. The results indicated that acetic acid inhibited the fermentation by C. shehatae NJ 23 markedly more than by bakers' yeast, whereas no significant difference in tolerance towards the compounds was detected between the S. cerevisiae strains. Furfural (2 g L-1) and the lignin derived compound p-hydroxybenzoic acid (2 g L-1) did not affect any of the yeasts at the cell mass concentration used. The results indicated that the linear model was not adequate to describe the experimental data (the p-values of curvatures were 0.048 for NJ 23 and 0.091 for bakers' yeast). Based on the results from the 2(3)-full factorial experiment, an extended experiment was designed based on a central composite design to investigate the influence of the factors on the specific growth rate (mu), biomass yield (Yx), volumetric ethanol productivity (QEtOH), and YEtOH. Bakers' yeast was chosen in the extended experiment due to its better tolerance towards acetic acid, which makes it a more interesting organism for use in industrial fermentations of lignocellulosic hydrolysates. The inoculum size was reduced in the extended experiment to reduce any increase in inhibitor tolerance that might be due to a large cell inoculum. By dividing the experiment in blocks containing fermentations performed with the same inoculum preparation on the same day, much of the anticipated systematic variation between the experiments was separated from the experimental error. The results of the fitted model can be summarised as follows: mu was decreased by furfural (0-3 g L-1). Furfural and acetic acid (0-10 g L-1) also interacted negatively on mu. Furfural concentrations up to 2 g L-1 stimulated Yx in the absence of acetic acid whereas higher concentrations decreased Yx. The two compounds interacted negatively on Yx and YEtOH. Acetic acid concentrations up to 9 g L-1 stimulated QEtOH, whereas furfural (0-3 g L-1) decreased QEtOH. Acetic acid in concentrations up to 10 g L-1 stimulated YEtOH in the absence of furfural, and furfural (0-2 g L-1) slightly increased YEtOH in the absence of acetic acid whereas higher concentrations caused inhibition. Acetic acid and furfural interacted negatively on YEtOH.

Acetic Acid↗
PubMed2006

Atmospheric oxidation pathways of acetic acid.

One of the most abundant carboxylic acids measured in the atmosphere is acetic acid (CH(3)C(O)OH), present in rural, urban, and remote marine environments in the low-ppb range. Acetic acid concentrations are not well reproduced in global 3-D atmospheric models because of the poor inventory of sources and sinks to model its global distribution. To understand the complete oxidation of acetic acid in the atmosphere initiated by OH radicals, ab initio calculations are performed to describe in detail the energetics of the reaction potential energy surface (PES). The proposed reaction mechanism suggests that the CH(3)C(O)OH + OH reaction takes place via three pathways: the addition of OH to the central carbon, the abstraction of a methyl hydrogen, and the abstraction of an acidic hydrogen. The PES is characterized by prereactive H-complexes, transition states, and more interestingly unique radical-mediated isomerization reactions. From the analysis of the energetics, acetic acid atmospheric oxidation will proceed mainly via the abstraction of the acidic hydrogen, consistent with previous experimental and theoretical studies. The major byproducts from each pathway are identified. Glyoxylic acid is suggested to be a major byproduct of the atmospheric oxidation of acetic acid. The atmospheric fate of glyoxylic acid is discussed.

Journal Article↗
PubMed2005

Synthesis and biological evaluation of new GABA-uptake inhibitors derived from proline and from pyrrolidine-2-acetic acid.

Several synthetic approaches to N-alkylated derivatives of 4-hydroxypyrrolidine-2-carboxylic acid and 4-hydroxypyrrolidine-2-acetic acid are described. The final compounds have been evaluated as potential inhibitors of the GABA transport proteins GAT-1 and GAT-3. The biological assays used were based on bovine material or porcine brain. As compared to the corresponding 4-unsubstituted compounds, the 4-hydroxypyrrolidine-2-carboxylic acid and 4-hydroxypyrrolidine-2-acetic acid derivatives showed a significant decrease in the inhibitory potency at both GAT-1 and GAT-3 with only four compounds having reasonable affinity to GAT-1 (IC(50): 5.1, 6.6 and 9.4 microM) or GAT-3 (IC(50): 19.9 microM), respectively. The biological data of the 4-hydroxypyrrolidine-2-acetic acid derivatives indicates that (2S)-configuration at the C-2 position for potent inhibition of GAT-1 and (4R)-configuration at the C-4 position for potent inhibition of GAT-3 may be crucial.

Animals↗
PubMedDate not supplied

Radiofrequency thermal ablation: increase in lesion diameter with continuous acetic acid infusion.

PURPOSE: To evaluate the influence of continuous infusion of acetic acid 50% during radiofrequency ablation (RFA) on the size of the thermal lesion produced. METHODS: Radiofrequency (RF) was applied to excised bovine liver by using an expandable needle electrode with 10 retractable tines (LeVeen Needle Electrode, RadioTherapeutics, Sunnyvale, CA) connected to a commercially available RF generator (RF 2000, RadioTherapeutics, Sunnyvale, CA). Experiments were performed using three different treatment modalities: RF only (n = 15), RF with continuous saline 0.9% infusion (n = 15), and RF with continuous acetic acid 50% infusion (n = 15). RF duration, power output, tissue impedance, and time to a rapid rise in impedance were recorded. The ablated lesions were evaluated both macroscopically and histologically. RESULTS: The ablated lesions appeared as spherical or ellipsoid, well-demarcated pale areas with a surrounding brown rim with both RF only and RF plus saline 0.9% infusion. In contrast, thermolesions generated with RF in combination with acetic acid 50% infusion were irregular in shape and the central portion was jelly-like. Mean diameter of the coagulation necrosis was 22.3 +/- 2.1 mm (RF only), 29.2 +/- 4.8 mm (RF + saline 0.9%) and 30.7 +/- 5.7 mm (RF + acetic acid 50%), with a significant increase in the RF plus saline 0.9% and RF plus acetic acid 50% groups compared with RF alone. Time to a rapid rise in impedance was significantly prolonged in the RF plus saline 0.9% and RF plus acetic acid 50% groups compared with RF alone. CONCLUSIONS: A combination of RF plus acetic acid 50% infusion is able to generate larger thermolesions than RF only or RF combined with saline 0.9% infusion.

Acetic Acid↗
PubMed2004

Enhanced expression of aconitase raises acetic acid resistance in Acetobacter aceti.

Acetobacter spp. are used for industrial vinegar production because of their high ability to oxidize ethanol to acetic acid and high resistance to acetic acid. Two-dimensional gel electrophoretic analysis of a soluble fraction of Acetobacter aceti revealed the presence of several proteins whose production was enhanced, to various extents, in response to acetic acid in the medium. A protein with an apparent molecular mass of 100 kDa was significantly enhanced in amount by acetic acid and identified to be aconitase by NH2-terminal amino acid sequencing and subsequent gene cloning. Amplification of the aconitase gene by use of a multicopy plasmid in A. aceti enhanced the enzymatic activity and acetic acid resistance. These results showed that aconitase is concerned with acetic acid resistance. Enhancement of the aconitase activity turned out to be practically useful for acetic acid fermentation, because the A. aceti transformant harboring multiple copies of the aconitase gene produced a higher concentration of acetic acid with a reduced growth lag-time.

Acetic Acid↗
PubMedDate not supplied

Individual cells of Saccharomyces cerevisiae and Zygosaccharomyces bailii exhibit different short-term intracellular pH responses to acetic acid.

The effects of perfusion with 2.7 and 26 mM undissociated acetic acid in the absence or presence of glucose on short-term intracellular pH (pH(i)) changes in individual Saccharormyces cerevisiae and Zygosaccharomyces bailii cells were studied using fluorescence-ratio-imaging microscopy and a perfusion system. In the S. cerevisiae cells, perfusion with acetic acid induced strong short-term pH(i) responses, which were dependent on the undissociated acetic acid concentration and the presence of glucose in the perfusion solutions. In the Z. bailii cells, perfusion with acetic acid induced only very weak short-term pH(i) responses, which were neither dependent on the undissociated acetic acid concentration nor on the presence of glucose in the perfusion solutions. These results clearly show that Z. bailii is more resistant than S. cerevisiae to short-term pH(i) changes caused by acetic acid.

Acetic Acid↗
PubMed2002

Effect of acetic acid consumption on clinical laboratory values in the dog.

To investigate the influence of food enriched with acetic acid on the clinical, biochemical, electrolyte, blood gas, haematological and urinary variables in the dog, a cross-over study was carried out with periods of approximately 2 weeks involving six healthy, adult dogs. Another objective was to determine the maximum concentration of acetic acid that the dogs found to be palatable. The dogs were maintained on a commercial meat-based food with added acetic acid and/or glucose. The administered acetic acid was increased in stages. All dogs accepted the diet containing acetic acid at a level of 5% of metabolizable energy. Except for a decrease in plasma total protein, none of the variables were significantly affected by acetic acid consumption. Acetic acid feeding did not affect plasma acetate concentration and urinary acetate excretion, indicating that dogs efficiently metabolize ingested acetic acid.

Acetic Acid↗
PubMed2006

Treatment of plantar fasciitis by LowDye taping and iontophoresis: short term results of a double blinded, randomised, placebo controlled clinical trial of dexamethasone and acetic acid.

OBJECTIVES: To determine if, in the short term, acetic acid and dexamethasone iontophoresis combined with LowDye (low-Dye) taping are effective in treating the symptoms of plantar fasciitis. METHODS: A double blinded, randomised, placebo controlled trial of 31 patients with medial calcaneal origin plantar fasciitis recruited from three sports medicine clinics. All subjects received six treatments of iontophoresis to the site of maximum tenderness on the plantar aspect of the foot over a period of two weeks, continuous LowDye taping during this time, and instructions on stretching exercises for the gastrocnemius/soleus. They received 0.4% dexamethasone, placebo (0.9% NaCl), or 5% acetic acid. Stiffness and pain were recorded at the initial session, the end of six treatments, and the follow up at four weeks. RESULTS: Data for 42 feet from 31 subjects were used in the study. After the treatment phase, all groups showed significant improvements in morning pain, average pain, and morning stiffness. However for morning pain, the acetic acid/taping group showed a significantly greater improvement than the dexamethasone/taping intervention. At the follow up, the treatment effect of acetic acid/taping and dexamethasone/taping remained significant for symptoms of pain. In contrast, only acetic acid maintained treatment effect for stiffness symptoms compared with placebo (p = 0.031) and dexamethasone. CONCLUSIONS: Six treatments of acetic acid iontophoresis combined with taping gave greater relief from stiffness symptoms than, and equivalent relief from pain symptoms to, treatment with dexamethasone/taping. For the best clinical results at four weeks, taping combined with acetic acid is the preferred treatment option compared with taping combined with dexamethasone or saline iontophoresis.

Acetic Acid↗