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PubMed1993

Antimicrobial activity of sulfur dioxide to certain lactic acid bacteria isolated from wines.

This study was conducted to investigate the relationship between pH and the toxicity of sulfur dioxide against homo- and hetero-lactic acid bacteria isolated from American acidic wines. Malolactic fermentation was found to be growth-associated in homo- and hetero-lactic strains. The pH of CBB broth had an insignificant effect on the specific death rate of these strains; the concentration of molecular sulfur dioxide had a great effect on the specific death rate and malate degradation. Laboratory or freshly isolated strains were exposed to various concentrations of free sulfur dioxide at pH 3.8 and 3.4. At pH 3.4, sulfur dioxide was more effective against lactic acid bacteria than at pH 3.8 since more was present as molecular sulfur dioxide and causing an increase in the specific death rate. Pediococcus strain BB was more resistant to sulfur dioxide than those hetero-lactic fermentation strains such as Leuconostoc oenos PSU-1 and ML-34. The effect of sulfur dioxide concentration on the viability of L. oenes ML-34, PSU-1, and Pediococcus strain BB appeared to be biphasic. No or little L-malic acid was degraded when the homo- and hetero-fermentative strains were killed by sulfur dioxide.

Hydrogen-Ion Concentration↗
PubMed2000

Effects of pH and concentration of citric, malic and lactic acids on enamel, in vitro.

OBJECTIVE: Dental erosion associated with soft drink consumption probably results from the contained dietary acids in the formulations. The pH value of any formulation is an important variable in acid erosion but not necessarily the only important factor. The aim of this study was to measure enamel erosion by citric, malic and lactic acids at pH values and acid concentrations representative of a range found in soft drink formulations and to determine the effect of adding calcium to citric acid. METHODS: Flat ground enamel samples were prepared from unerupted human third molar teeth. Groups of five specimens were placed in citric, malic and lactic acid solutions of different pH and acid concentration for three by 10 min exposures at 35 degrees C. Enamel loss was measured by profilometry. Enamel specimens were also exposed to citric acid solutions containing calcium at different pH values and at the same pH with different concentrations of calcium. RESULTS: Numerical data and contour plots for each acid showed a similar pattern for increasing erosion with decreasing pH and increasing acid concentration and vice versa for decreasing erosion. Increasing the concentration of calcium in a fixed pH citric acid solution resulted in decreased erosion. This effect was most marked at higher pH. CONCLUSIONS: This study has shown that under highly controlled conditions the erosion of enamel by solutions of dietary acids is influenced by the interplay of pH, acid concentration and presence of calcium. These variables and in particular the concentration of calcium could be manipulated to produce soft drinks with reduced erosivity to enamel.

Beverages↗
PubMedDate not supplied

Antitumor effect of geranylamine derivatives on human hepatoma.

In this study, we examined the antitumor activities of isoprenoid derivatives conjugated with substrates of energy metabolism in human hepatoma-bearing athymic mice. Among these compounds, N-geranylpyruvic amide, N-geranyl-p-pyruvaminobenzoic amide, N,N'-digeranylmalic diamide and N,N'-digeranyl-O-acetylmalic diamide had strong antitumor effects. These geranylamine derivatives also inhibited in vitro cell growth. Sugar conjugates of geranylamine, geranic acid and mevalonic acid did not show any antitumor effect in vivo or in vitro. Although the geranylamine derivatives had no impact on the cell cycle distribution at 24 h, a sub-G1 (apoptotic) peak of varying magnitude was seen in DNA histograms of cells treated with the derivatives for 48 h. However, the geranylamine derivatives did not inhibit protein isoprenylation, which has been reported in cancer cells treated with several natural isoprenoids. These results suggest that the geranylamine derivatives conjugated with malic acid and pyruvic acid have a different mechanism of antitumor activity from that of natural isoprenoids.

Animals↗
PubMed2003

Modifications to the silver physical developer.

The silver physical developer is currently the most successful reagent used for visualizing the water-insoluble components (e.g., lipids) of latent prints on porous surfaces. It is normally used after the amino acid visualizing reagents (e.g., ninhydrin and DFO) are used. This work found that the performance of the current formulation of silver physical developer is strongly reduced when the water used is changed from the usual distilled water to the more purified reverse osmosis/deionized (RO/DI) water. Based on numerous experiments involving the systematic variation of the component concentrations, the performance was restored and even improved by reducing the concentration of all the components (except that of the ferric salt) and by including malic acid in the formulation. These modifications resulted in a new silver physical developer formulation that performs as well as or better than the current formulation and is less expensive to make.

Dermatoglyphics↗
PubMed1992

Fluorescence Quenching in the Varied Photosynthetic Modes of Portulacaria afra (L.) Jacq.

The kinetics of chlorophyll fluorescence were measured in Portulacaria afra (L.) Jacq. when the plants were functioning in either Crassulacean acid metabolism (CAM) or C(3)/CAM cycling (called cycling) modes, as determined by fluctuation in titratable acidity and gas exchange properties. Cycling plants showed primarily daytime CO(2) uptake typical of C(3) plants, but with a slight diurnal acid fluctuation, whereas CAM plants showed nocturnal CO(2) uptake, daytime stomatal closure, and a large diurnal acid fluctuation. Results from fluorescence measurements indicated no significant differences in photochemical quenching between cycling and CAM plants; however, sizable differences were detected in nonphoto-chemical quenching (q(n)), with the largest differences being observed during the middle of the day. Cycling plants had lower q(n) than CAM plants, indicating altered photosynthetic regulation processes. This q(n) difference was believed to be related to reduced internal CO(2) concentration in the CAM plants because of daytime stomatal closure and reduced deacidification rates in the late afternoon when most of the malic acid has been utilized. Experimentally, higher external CO(2) given to plants in the CAM mode resulted in a decline in q(n) in comparison to that measured in plants in the cycling mode. No changes were observed in photochemical quenching when CO(2) was added.

Journal Article↗
PubMed1994

Histamine production by wine lactic acid bacteria: isolation of a histamine-producing strain of Leuconostoc oenos.

Populations of Leuconostoc oenos were harvested from wines containing a relatively high concentration of biogenic amines. Cultivation of the biomass in synthetic media and wine showed that it consisted of histamine-producing strains. Histamine levels after culture depended on the quantity of precursor available and on the presence of yeast lees, which certainly enriched the medium in histidine. Ethanol and pH, which control bacterial growth rate and total population, were also significant factors: pH and low ethanol concentration enhanced histamine production. Strain Leuc. oenos 9204 was isolated and studied since it retained its ability to produce histamine after several transfers. In synthetic medium this strain produced large amounts of histamine especially in the poorest nutritional conditions (no glucose, no L-malic acid). These results clearly demonstrate that Leuc. oenos involved in wine-making might play a role in biogenic amine production. The vinification method might also influence the final amine concentration in wine.

Biogenic Amines↗
PubMed2006

Use of the 1H nuclear magnetic resonance spectra signals from polyphenols and acids for chemometric characterization of cider apple juices.

The low field region (5.8-9.0 ppm) corresponding to aromatic protons and the region 1.8-3.0 ppm of the (1)H NMR spectra were used for characterization and chemometric differentiation of 52 apple juices obtained from six cider apple varieties. The data set consisted of 14 integrated areas corresponding to resonances from acids and phenolic compounds. Multivariate procedures based on hierarchical cluster and discriminant analysis were performed on selected signals of the spectra to determine whether it was possible to distinguish the different juices. Cluster analysis was able to satisfactorily classify the six apple varieties. Discriminant analysis, by means of stepwise procedure for variables selection and leave-one-out for cross-validation, was applied to 40 samples from the year 2001, obtaining recognition and prediction abilities of 100%. The most discriminant variables corresponded to poliphenols, (-)-epicatechin, phloridzin-phloretin, and p-coumaric, chlorogenic, and malic acids. The classification model was applied to 12 samples from apples harvested in the years 2002 and 2003, and the prediction ability was 91.7%.

Beverages↗
PubMed1987

Reduction State of Q and Nonradiative Energy Dissipation during Photosynthesis in Leaves of a Crassulacean Acid Metabolism Plant, Kalanchoë daigremontiana Hamet et Perr.

Fluorescence was measured in leaves of the CAM plant Kalanchoë daigremontiana using a pulse modulation technique at room temperature. During a 12-h light period at 500 micromole photons per square meter per second (400-700 nanometers) in air containing 350 microbar CO(2), the component of fluorescence quenching related to the reduction state of Q, the primary electron transport acceptor of PSII, remained fairly constant and showed that only 20% of Q were in the reduced form. The reduction state was slightly increased at the onset and at the end of the light period. By contrast, the nonphotochemical component of fluorescence quenching which is a measure of the fraction of nonradiative deexcitation underwent marked diurnal changes. Nonradiative energy conversion was low during the phase of most active malic acid decarboxylation in the middle of the light period when uptake of atmospheric CO(2) was negligible, and when internal CO(2) partial pressures were higher than in air; this allowed for high rates of CO(2) reduction in the chloroplasts. Nonradiative energy conversion was high during the early and the late light period when atmospheric CO(2) was taken up and internal CO(2) partial pressures were below air level. Manipulation of the internal CO(2) partial pressure during the late light period by increasing or decreasing the external CO(2) partial pressure to 1710 and 105 microbar, respectively, led to changes in the magnitude of energy dependent fluorescence quenching which were consistent with the relationship between nonradiative energy dissipation and internal CO(2) partial pressure observed during the diurnal cycle. Again, the reduction state of Q was hardly affected by these treatments. Thus, changes in electron transport rate during the diurnal CAM cycle at a given photon flux density lead primarily to alterations in the rate of nonradiative energy dissipation, with the reduction state of Q being maintained at a relatively low and constant level. Conditions are described under which nonphotochemical dissipation of excitation energy reaches a maximum value and the reduction state of Q is increased.

Journal Article↗
PubMed1998

Physicochemical Characteristics of Selected Sweet Cherry Cultivars.

The volatile, sugar, and organic acid constituents in 12 cultivars and selections of sweet cherries (Prunus avium L.) were characterized and quantified by high-performance liquid chromatography and gas chromatography (GC). Fruit weight, soluble solids concentration (SSC), pH, titratable acidity (TA), and color (CIE L, a, b) were also determined at harvest. Weight ranged from 8.8 to 14.5 g per fruit, SSC from 13.5 to 24.5 degrees Brix, and SSC/TA ratio from 18.3 to 29.0. Chroma was a better indicator of color variations among sweet cherry cultivars compared to the hue angle as it correlated highly with L, a, and b values (r > 0.90). The major nonvolatile constituents varied widely among cultivars: glucose [5.2-8.8 g/100 g of fresh weight (FW)], fructose (4.4-6.4 g/100 g of FW), sorbitol and mannitol (2.2-8.0 g/100 g of FW), and malic acid (502.7-948.3 mg/100 g of FW). Three principal components accounted for 53.3% of the total variation among 50 volatile compounds assessed by a dynamic headspace GC method. (E)-2-Hexenol, benzaldehyde, hexanal, and (E)-2-hexenal were predominant flavor volatiles and could be used to segregate commercial and new cherry selections into various subgroups.

Journal Article↗
PubMed1995

Treatment of fibromyalgia syndrome with Super Malic: a randomized, double blind, placebo controlled, crossover pilot study.

OBJECTIVE: To study the efficacy and safety of Super Malic, a proprietary tablet containing malic acid (200 mg) and magnesium (50 mg), in treatment of primary fibromyalgia syndrome (FM). METHODS: Twenty-four sequential patients with primary FM were randomized to a fixed dose (3 tablets bid), placebo controlled, 4-week/course, pilot trial followed by a 6-month, open label, dose escalation (up to 6 tablets bid) trial. A 2-week, medication free, washout period was required before receiving treatment, between blinded courses, and again before starting open label treatment. The 3 primary outcome variables were measures of pain and tenderness but functional and psychological measures were also assessed. RESULTS: No clear treatment effect attributable to Super Malic was seen in the blinded, fixed low dose trial. With dose escalation and a longer duration of treatment in the open label trial, significant reductions in the severity of all 3 primary pain/tenderness measures were obtained without limiting risks. CONCLUSIONS: These data suggest that Super Malic is safe and may be beneficial in the treatment of patients with FM. Future placebo-controlled studies should utilize up to 6 tablets of Super Malic bid and continue therapy for at least 2 months.

Cross-Over Studies↗
PubMed1966

CO(2) Fixation in Opuntia Roots.

Nonautotrophic CO(2) metabolism in Opuntia echinocarpa roots was studied with techniques of manometry and radiometry. The roots were grown in a one-quarter strength nutrient solution for several days; the distal 2 cm was used for physiological studies. The roots assimilated significant quantities of (14)CO(2) and appeared to show a crassulacean-type acid metabolism with respect to quality and quantity. Most of the (14)C activity was associated with the distal portion of the elongating root indicating correlation with metabolic activity. The (14)CO(2) assimilation was comparable to a crassulacean leaf succulent, but 3 times greater than that found for stem tissue of the same Opuntia species.The rates of O(2) and CO(2) exchange and estimated CO(2) fixation were 180, 123, and 57 mul/g per hour. A respiratory quotient of 0.66 was found.The products of (14)CO(2) fixation were similar in most respects to reported experiments with leaf succulents. Equilibration of the predominant malic acid with isocitric, succinic, and fumaric acids was not evident. The latter observation was interpreted as metabolic isolation of the fixation products rather than poor citric acid cycle activity.A rapid turnover of the fixed (14)CO(2) was measured by following decarboxlyation kinetics and by product analysis after a postincubation period. The first order rate constant for the steady state release was 4.4 x 10(-3) min(-1) with a half-time of 157.5 minutes. Amino acids decayed at a more rapid rate than organic acids.

Journal Article↗
PubMed1987

Fructose 2,6-bisphosphate, carbohydrate partitioning, and crassulacean Acid metabolism.

Fructose 2,6-bisphosphate (F 2,6-P(2)) was detected in the CAM species, Ananas comosus and Bryophyllum tubiflorum, and in C(3)- and CAM-Mesembryanthemum crystallinum. In both Mesembryanthemum tissues, F 2,6-P(2) was located outside the chloroplast. The levels of F 2,6-P(2), malate, starch, or soluble sugars were measured during various periods during the day-night cycle in the leaves of Ananas, a species which stores carbohydrate in an extrachloroplastic compartment, and in Bryophyllum, a species which stores carbon as starch in the chloroplast. In both species, the levels of F 2,6-P(2) were correlated with the stages of the day-night CAM cycle. Immediately following the dark-light transition the F 2,6-P(2) levels exhibited a rapid transient increase followed by a decrease. F 2,6-P(2) reached a daily minimum soon after the onset of deacidification and remained low until the malic acid pools approached their daily minima; the levels of F 2,6-P(2) then began a slow increase which accelerated during the period of afternoon CO(2) uptake. Immediately following the light-dark transition F 2,6-P(2) levels fluctuated. The levels were usually low after the fluctuations had ceased. The pools then increased as the rate of malate synthesis increased, remained at relatively constant high levels when the rates of malate synthesis were constant, and decreased as malate synthesis decreased towards the end of the dark period. The absolute levels of F 2,6-P(2) were always higher in Ananas than in Bryophyllum. The ratios of the activity of pyrophosphate fructose-6-phosphate l-phosphotransferase to cytoplasmic fructose 1,6-bisphosphatase and to phosphofructokinase were also far higher in Ananas than in Bryophyllum or in C(3)- or CAM-Mesembryanthemum.

Journal Article↗
PubMed2003

The effect of SO2 on the production of ethanol, acetaldehyde, organic acids, and flavor volatiles during industrial cider fermentation.

SO(2) is widely used in cider fermentation but also in other alcoholic beverages such as wine. Although the authorized limit is 200 ppm total SO(2), the International Organizations recommend its total elimination or at least reduction due to health concerns. Addition of SO(2) to apple juice at levels frequently used in industrial cidermaking (100 mg/L) induced significantly higher acetaldehyde production by yeast than that obtained without SO(2). Although the practical implications of acetaldehyde evolution under cidermaking conditions has been overcome by research and few data are available, this compound reached levels in two 2000 L bioreactors that may have prevented the occurrence of simultaneous alcoholic and malolactic fermentation. It was observed that malolactic fermentation had a positive effect promoting reduction of acetaldehyde levels in cider fermented with juice, SO(2)-treated or not. The addition of SO(2) clearly delayed malolactic fermentation comparing to the control, affecting not the onset of the malolactic fermentation but the rate of malic acid degradation. This compound, however, had a stimulatory effect on alcoholic fermentation.

Acetaldehyde↗
PubMed1990

Renin inhibitory peptides. A beta-aspartyl residue as a replacement for the histidyl residue at the P-2 site.

In an effort to decrease the size and to increase the hydrophilicity of the previously prepared renin inhibitory peptides, it was postulated that one might be able to take advantage of the polar Thr-84 on the flap region of the enzyme renin by potential hydrogen bonding to polar functionality on the inhibitory peptide at the P-2 site. A beta-aspartyl residue with a carboxylic acid group was proposed to be a possible replacement for the histidyl residue at the P-2 site. A series of renin inhibitory peptides were prepared with the beta-aspartyl residue to probe the structure-activity relationship of the resulting peptides. Potent inhibitory peptides could be realized with activity in the subnanomolar range. Molecular modeling was also undertaken to investigate the interactions between the enzyme active site and the new inhibitors and to suggest a possible mode of binding of these ligands to the enzyme. From this modeling study, the role of Ser-229 at the active site in the bound conformer of the inhibitors was suggested. It was further noted in the analogue study that a malic acid residue, which is the oxygen analogue of the beta-aspartic acid residue, could lead to further enhancement of inhibitory potency of congeneric peptides. Small renin inhibitors, such as compound XII with molecular weight 535 and with no alpha-amino acid residue, could be prepared and exhibited renin inhibitory activity in the nanomolar range.

Aspartic Acid↗
PubMed1969

Assimilation and metabolism of exogenous organic compounds by the strict autotrophs Thiobacillus thioparus and Thiobacillus neapolitanus.

The assimilation and utilization of the individual carbon atoms of pyruvate and acetate by cells of Thiobacillus thioparus and T. neapolitanus, in the presence and absence of an energy source, were studied by use of radioactive substrates. Both organisms produced (14)CO(2) from (14)C-labeled pyruvate, but more came from carbon 1 than from carbons 2 or 3. The conversion of the carbons of acetate to CO(2) by both organisms was much less than that from any of the pyruvate carbons. When labeled pyruvate and acetate were incubated with these organisms, small amounts of radioactivity were found in the tricholoacetic acid-soluble material, nucleic acids, and lipids, and larger amounts were found in the protein fraction. The composition of the incubation medium affected the amount of utilization and incorporation of labeled substrates by both organisms. The presence of an exogenous energy source (Na(2)S(2)O(3)) suppressed incorporation of the labeled substrates into various cellular components by T. thioparus, but enhanced incorporation by T. neapolitanus. When (14)C-pyruvate was used as a substrate, as many as 12 radioactive compounds were found in the water-soluble fraction in the experiments with T. neapolitanus, whereas no more than three radioactive compounds were detected in this fraction in the experiments with T. thioparus. Of the total (14)C activity found in the water-soluble fractions, malic acid contained the highest percentage. These findings are discussed in light of the overall metabolism of these two sulfur-oxidizing obligate chemoautotrophs, as well as in relation to the biochemical basis of chemoautotrophy.

Acetates↗
PubMed2000

Gustatory responsiveness to food-associated sugars and acids in pigtail macaques, Macaca nemestrina.

Taste-preference thresholds for five food-associated sugars and acids, respectively, as well as relative sweet-taste preferences were assessed in six pigtail macaques using two-bottle choice tests of brief duration (1 min). In experiment 1, the animals were found to significantly prefer concentrations as low as 10 mM maltose and sucrose, 20 mM fructose and glucose, and 30 mM lactose over tap water. In experiment 2, the monkeys were given a choice between all binary combinations of the same five saccharides presented in equimolar concentrations of 50, 100, 200, and 400 mM. Preferences for individual sugars were stable across the concentrations tested and indicate the following order of relative effectiveness: maltose>sucrose>glucose> or =fructose> or =lactose. In experiment 3, Macaca nemestrina was found to significantly discriminate concentrations as low as 5 mM malic acid, 10 mM ascorbic acid, 20 mM citric acid and acetic acid, and 0.5 mM tannic acid from the alternative stimulus. With the latter substance, the monkeys rejected all suprathreshold concentrations tested, whereas with the former four substances, the animals showed an inverted U-shaped function of preference. The results showed pigtail macaques to be the first primate species tested so far whose taste-preference threshold for maltose is as low as that for sucrose, and which - similar to rodents - prefers maltose over equimolar concentrations of sucrose and other saccharides. Further, unlike most other primates, pigtail macaques do not generally reject acidic tastants but show a substance- and concentration-dependent change in their behavioral response that may range from rejection to preference. The results support the assumption that the gustatory responsiveness of M. nemestrina to food-associated sugars and acidic tastants might reflect an evolutionary adaptation to its dietary habits.

Acetic Acid↗
PubMed1999

The Effect of Elevated Concentrations of Fructose 2,6-Bisphosphate on Carbon Metabolism during Deacidification in the Crassulacean Acid Metabolism Plant Kalanchöe daigremontiana.

In C(3) plants, the metabolite fructose 2,6-bisphosphate (Fru 2,6-P(2)) has an important role in the regulation of carbon partitioning during photosynthesis. To investigate the impact of Fru 2,6-P(2) on carbon metabolism during Crassulacean acid metabolism (CAM), we have developed an Agrobacterium tumefaciens-mediated transformation system in order to alter genetically the obligate CAM plant Kalanchöe daigremontiana. To our knowledge, this is the first report to use genetic manipulation of a CAM species to increase our understanding of this important form of plant metabolism. Transgenic plants were generated containing a modified rat liver 6-phosphofructo-2-kinase gene. In the plants analyzed the activity of 6-phosphofructo-2-kinase ranged from 175% to 198% of that observed in wild-type plants, resulting in Fru 2,6-P(2) concentrations that were 228% to 350% of wild-type plants after 2 h of illumination. A range of metabolic measurements were made on these transgenic plants to investigate the possible roles of Fru 2,6-P(2) during Suc, starch, and malic acid metabolism across the deacidification period of CAM. The results suggest that Fru 2,6-P(2) plays a major role in regulating partitioning between Suc and starch synthesis during photosynthesis. However, alterations in Fru 2,6-P(2) levels had little effect on malate mobilization during CAM fluxes.

Journal Article↗
PubMed2006

Seasonal variation of microbial ecology in hemlock soil of Tatachia Mountain, Taiwan.

BACKGROUND AND PURPOSE: Forest soil microorganisms and fauna decompose the organic materials, and thus strongly influence the nutrient cycling of the ecosystem. Soil microorganisms also contribute to soil structure and soil fertility. In Taiwan, the microbial distributions of soils have only been determined in acidic soil, inorganic acidic soil, upland soil, alkaline soil and power plant areas. There are few data on the microbial populations of forest soils. Tatachia Mountain is located in the central part of Taiwan and is a typical high altitude protected ecosystem area, designated as a National Park. This study investigated the role of microorganisms in the ecology and nutrient transformation of forest soil in Taiwan. METHODS: As part of long-term ecological research in Taiwan, the environmental conditions, seasons, microbial populations, biomass and organic acid contents of hemlock soil were investigated. We also studied the effect of depth on microbial populations and biomass. RESULTS: The soil temperatures were between 5.5 and 15.6 degrees C and the soil pH ranged from 3.3 to 4.4. Total organic carbon and total nitrogen contents ranged from 2.3 to 37.1% and from 0.3 to 1.7%, respectively. The carbon/nitrogen ratio was between 8.2 and 24.4. In topsoil, each gram of soil contained 10(5)-10(7) colony-forming units (CFU) culturable bacteria, 10(2)-10(5) CFU actinomycetes, 10(3)-10(5) CFU fungi, 10(4)-10(6) CFU cellulolytic microbes, 10(4)-10(6) CFU phosphate-solubilizing microbes, and 10(3)-10(6) CFU nitrogen-fixing microbes. Microbial populations were higher in topsoil compared with subsoil, but lower in topsoil than in organic layer. Microbial populations also decreased with the depth of soil. Microbial populations at 1E horizon were 0.6% to 9.4% of those at O horizon. The microbial biomass evaluated contained carbon 391-1013 mug, nitrogen 51-146 mug, malic acid 76-557 nM and succinic acid 37-527 nM per gram of soil. Summer season had higher microbial populations, biomass and organic content than winter season, but the differences were not significant. CONCLUSION: Heavy coverage of organic matter was found in hemlock and spruce soils and was associated with acidic pH. Microbial populations decreased with increasing soil depth. Microbes play a very important role in organic matter decomposition and nutrition transformation in hemlock soil.

Actinobacteria↗