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PubMed1982

Transport of the herbicide 3-amino-1,2,4-triazole by cultured tobacco cells and leaf protoplasts.

Transport of the herbicide amitrole (3-amino-1,2,4-triazole) by suspension cultured cells and leaf protoplasts of Nicotiana tabacum cv. Wisconsin 38 has been investigated. Cells were batch-cultured and routinely assayed 3 days after subculturing. Uptake rate was pH-independent, energy independent, and culture growth phase-dependent, with growing cells exhibiting the highest rates. At a concentration of 0.2 millimolar amitrole, uptake rates yielded a Q(10) of 1.6 in the 18 to 28 degrees C temperature range. Amitrole was not concentrated over a 48-hour period and showed unsaturable kinetics over the concentration range of 0.01 to 50.0 millimolar. Uptake was not significantly influenced by a 100-fold higher concentration of several amino acids (l-Asp, gamma-amino-n-butyric acid, l-His, l-Leu, l-Met, l-Trp), sucrose, glucose, fructose, and oxaloacetic acid. Uptake rate inhibition by malic acid and stimulation by NH(4)SCN were statistically significant. Amitrole was bound to cellular material, but uptake of amitrole by tobacco leaf protoplasts demonstrated that cell walls did not qualitatively influence uptake. These results indicate that amitrole enters the cells via simple diffusion.

Journal Article↗
PubMed2001

In vitro antimicrobial activities of bakuchiol against oral microorganisms.

Bakuchiol was isolated from the seeds of Psoralea corylifolia, a tree native to China with various uses in traditional medicine, followed by extraction with ether and column chromatography combined with silica gel and octyldecyl silane. In this study, the antimicrobial activities of bakuchiol against some oral microorganisms were evaluated in vitro. The cell growth of Streptococcus mutans was inhibited in a bakuchiol concentration-dependent manner, and growth of S. mutans was completely prevented by 20 microg of bakuchiol per ml. The bactericidal effect of bakuchiol on S. mutans was dependent on temperature and stable under the following conditions: sucrose, 0 to 10% (wt/vol); pH, 3.0 to 7.0; organic acids (3% [wt/vol] citric and malic acids). Bakuchiol showed bactericidal effects against all bacteria tested, including S. mutans, Streptococcus sanguis, Streptococcus salivarius, Streptococcus sobrinus, Enterococcus faecalis, Enterococcus faecium, Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus plantarum, Actinomyces viscosus, and Porphyromonas gingivalis, with MICs ranging from 1 to 4 microg/ml and the sterilizing concentration for 15 min ranging from 5 to 20 microg/ml. Furthermore, bakuchiol was also effective against adherent cells of S. mutans in water-insoluble glucan in the presence of sucrose and inhibited the reduction of pH in the broth. Thus, bakuchiol would be a useful compound for development of antibacterial agents against oral pathogens and has great potential for use in food additives and mouthwash for preventing and treating dental caries.

Anti-Bacterial Agents↗
PubMed2002

Consumer acceptance of raw apples treated with an antibacterial solution designed for home use.

An antibacterial treatment consisting of 1.5% lactic acid plus 1.5% hydrogen peroxide at 40 degrees C for 15 min was effective in reducing foodborne bacterial pathogens on raw apples. However, the effects of this treatment on an apple's sensory characteristics and the extent of consumers' willingness to use the treatment at home were not known. This study was undertaken to determine the sensory acceptability and chemical characteristics (pH, soluble solids, and total acidity) of apples subjected to the sanitizing treatment and to obtain information on consumers' purchase behavior, apple handling and consumption practices, and willingness to use an antibacterial treatment. Untrained consumers (n = 80) evaluated the appearance, color, aroma, flavor, texture, and overall appeal of untreated (control) and treated Red Delicious apples that had been stored at 5 degrees C for 0, 6, and 10 days. Panelists used a nine-point hedonic scale (1 = "dislike extremely"; 5 = "neither like nor dislike"; 9 = "like extremely") to evaluate sensory acceptability. Treatment and storage had no significant effect on the appearance, color, or aroma of the samples. Flavor ratings ranged from 6.2 ("like slightly") to 7.0 ("like moderately"). There was no significant difference among any of the control and treated apples stored for 0 days or among those stored for 6 days. Although apples stored for 10 days received the lowest ratings (6.2 to 6.3), they still had an acceptable flavor (6, "like slightly"), and panelists could not perceive differences between the control samples and the treated samples on day 10. The same trends were noted in texture ratings and in overall liking ratings. Treatment and storage had a minimal effect on pH (range, 3.96 to 4.02), soluble solids (range, 11.8 to 12.9 degrees Brix), and total acidity (range, 0.20 to 0.23% malic acid), which are important for apple flavor. Many consumers (87%) were concerned about fruit safety, and 53.2% were willing to try an antibacterial treatment at home. However, 74% would not be willing to use it if a 15-min heating-and-soaking step were required. Implementation of the treatment may be more feasible in the packinghouse than in the home.

Consumer Behavior↗
PubMed1995

Influence of hydroxycarboxylic acids on the water solubility of various bismuth compounds.

In an equilibrium dialysis assay (bismuth being determined by atomic absorption spectrometry) a constant amount of bismuth (Bi, CAS 7440-69-9) (final maximum conc. 50 mumol Bi/l) was dialyzed against solutions with increasing concentrations of the chelators (0-25 mmol/l). At pH 5, 50% of Bi(III) nitrate was soluble in solutions with 0.3, 6.3, 13.4 and 14.6 mmol/l of edetic acid (EDTA), citric, tartaric and malic acid, respectively. At the highest concentration applied, lactic acid kept 7% of bismuth in solution. Without any chelator, bismuth was found to be essentially insoluble (limit of detection: approx. 4 nmol Bi/l). A concentration-dependent increase in solubility was found also for the other bismuth compounds; the sequence of the solubilizing capacity of the chelators was the same as for Bi(III) nitrate. Lowering the pH to 3 generally increased and raising the pH to 7, decreased the solubility of bismuth.

Bismuth↗
PubMedDate not supplied

Conversion of fumaric acid to L-malic by sol-gel immobilized Saccharomyces cerevisiae in a supported liquid membrane bioreactor.

Conversion of fumaric acid (FA) to L-malic acid (LMA) was carried out in a bioreactor divided by two supported liquid membranes (SLMs) into three compartments: Feed, Reaction, and Product. The Feed/Reaction SLM, made of tri-n-octylphosphine oxide (vol 10%) in ethyl acetate, was selective toward the substrate, fumaric acid (S(FA/LMA) = 10). The Reaction/Product SLM, made of di(2-ethylhexyl) phosphate (vol 10%) in dichloromethane, was selective toward the product, L-malic acid (S(LMA/FA) = 680). Immobilized yeast engineered to overproduce the enzyme fumarase [E.C. 4.2.1.2] was placed in the Reaction compartment and served as the catalyst. The yeast was immobilized in small glasslike beads of alginate-silicate sol-gel matrix. The construction of the bioreactor ensured unidirectional flow of the substrate from the Feed to the Reaction and of the product from the Reaction to the Product compartments, with the inorganic counterion traveling in the opposite direction. The conversion of almost 100%, above the equilibrium value of ca. 84% and higher than that for the industrial process, 70%, was achieved. In contrast to the existing industrial biocatalytic process resulting in L-malic acid salts, direct production of the free acid is described.

Bioreactors↗
PubMed1965

Organic acid production by Basidiomycetes. I. Screening of acid-producing strains.

Sixty-seven strains belonging to 47 species of Basidiomycetes were examined for their acid-producing abilities in glucose media, in both the presence and absence of CaCO(3), in stationary and shake cultures. Some strains were found to produce large quantities of oxalic acid. The oxalic acid-producing strains could be separated into two groups. Strains of one group (mostly brown-rot fungi) were able to produce oxalic acid, regardless of whether CaCO(3) was present in the medium. Strains of the other group (mostly white-rot fungi) were characterized by their ability to produce oxalic acid only when CaCO(3) was added to the medium. With the latter group, shake-culturing was generally more effective than stationary culturing in respect to acid production. In the CaCO(3)-containing media, Schizophyllum commune, Merulius tremellosus, and Porodisculus pendulus were found to produce substantial amounts of L-malic acid as a main metabolic product, along with small quantities of oxalic and other acids in shake cultures. Especially, S. commune and M. tremellosus may be employed as malic acid-producing species.

Acids↗
PubMed2001

Role of extracellular peroxidase in the superoxide production by wheat root cells.

Extracellular peroxidase has been shown to contribute to superoxide production in wounded wheat (Triticum aestivum L. cv. Ljuba) root cells. The superoxide-synthesizing system of root cells was considerably inhibited by KCN and NaN3 and activated by MnCl2 and H2O2. Treatment of roots with salicylic acid and a range of di- and tri-carbonic acids (malic, citric, malonic, fumaric, and succinic acids) stimulated superoxide production in both root cells and extracellular solution. The H2O2-stimulated superoxide production in the extracellular solution was much higher when roots were preincubated with salicylic or succinic acid. Exogenous acids enhanced peroxidase activity in the extracellular solution. Pretreatment of root cells with the detergents trypsin and sodium dodecyl sulfate had similar effects on the peroxidase activity. Significant inhibition of both superoxide production and peroxidase activity by diphenylene iodonium suggests that the specificity of the latter as an inhibitor of NADPH oxidase is doubtful. Results obtained indicate that extra-cellular peroxidase is involved in the superoxide production in wheat root cells. The mobile form of peroxidase can be readily secreted to the apoplastic solution and serve as an emergency enzyme involved in plant wound response.

Adrenochrome↗
PubMed2002

Effects of exogenous propylene on softening, glycosidase, and pectinmethylesterase activity during postharvest ripening of apricots.

Apricots (Prunus armeniaca L. cv. Boccuccia spinosa) picked at the commercial ripening stage [soluble solids content (SSC) 12.6%] were left to reach full ripening in continuously humidified air at 20 degrees C. Changes in the rate of ethylene production, firmness, soluble solids concentration, and titratable acidity were measured. The alpha-D- and beta-D-glucosidases, alpha-L-arabinofuranosidase, alpha-D- and beta-D-galactosidases, beta-D-xylosidase, and alpha-D-mannosidase activities were assayed. To evaluate the influence of ethylene on glycosidase activity, propylene (500 microL x L(-1)) was applied to apricots for 24 and 48 h. In apricots ripened in air, ethylene production increased on the first day and exhibited a typical climacteric pattern. Good edible quality was reached in 5 days when SSC was at least 14% and acidity was between 1.1 and 1.2% (% malic acid). During postharvest ripening, alpha-L-arabinofuranosidase activity increased from 1.9 to 11.6 nkat until day 7. alpha-D-Galactosidase, alpha-D-mannosidase, and beta-D-galactosidase activity increased continuously but at a lower rate. beta-D-Xylosidase activity also increased, but the level of activity was lower than the other glycosidases assayed. Pectinmethylesterase (PME) decreased during the postharvest ripening, and propylene enhanced this pattern, by stimulating ethylene production. Even the activities of alpha-L-arabinofuranosidase, beta-D-xylosidase, alpha-D-mannosidase, and beta-D-galactosidase were greatly stimulated by the propylene treatment, which consequently induced rapid softening of the fruits.

Alkenes↗
PubMed2003

Changes in sugars, acids, and volatiles during ripening of koubo [Cereus peruvianus (L.) Miller] fruits.

The columnar cactus Cereus peruvianus (L.) Miller, Cactaceae (koubo), is grown commercially in Israel. The unripe fruits are green, and the color changes to violet and then to red when the fruit is fully ripe. The content of soluble sugars was found to increase 5-fold during ripening. Glucose and fructose were the main sugars accumulated in the fruit pulp, and each increased from 0.5 to 5.5 g/100 g fresh weight during ripening. The polysaccharides content decreased during ripening from 1.4 to 0.4 g/100 g fresh weight. The titratable acidity decreased and the pH increased during ripening. The major organic acid found in the fruit was malic acid, which decreased from 0.75 g/100 g fresh weight at the mature green stage to 0.355 g/100 g fresh weight in ripe fruits. Citric, succinic, and oxalic acids were found in concentrations lower than 0.07 g/100 g fresh weight. Prominent accumulation of aroma volatiles occurred toward the end of the ripening process. The main volatile found in the ripe fruit was linalool, reaching concentrations of 1.5-3.5 microg/g fresh weight.

Acids↗
PubMed2005

Compositional and sensory characteristics of three native sun-dried date (Phoenix dactylifera L.) varieties grown in Oman.

Three native sun-dried date varieties grown in Oman, namely, Fard, Khasab, and Khalas, were examined for their proximate composition, sugars, dietary fiber, minerals, and organic acids as well as sensory characteristics. The study was conducted on sun-dried dates due to their higher consumption compared with fresh dates. All results are expressed as mean value +/- standard deveiation (n = 3) on a fresh weight basis except for sensory analysis. Date varieties were found to be low in fat and protein, but rich in sugars, dietary fiber, and minerals. They were found to be a good source of energy (278-301 kcal/100 g), due to the high sugar content. Total sugar content ranged from 56.1 to 62.2 g/100 g, being lowest in Khasab and highest in Khalas. Total dietary fiber content of dates varied from 6.26 to 8.44 g/100 g, of which 84-94% was insoluble fiber. Twelve minerals were studied in dates, among which the major minerals were potassium, calcium, magnesium, and phosphorus. Date varieties were also found to be an excellent source of selenium (ranging from 0.36 to 0.53 mg/100 g). Six organic acids were positively identified, among which malic acid predominated in all varieties. Differences (p < 0.05) in the contents of dietary fiber, organic acids, and certain minerals were observed among the three date varieties examined. Descriptive sensory analysis showed that among the nine sensory attributes studied, only the attributes color and desirability were rated as being of significantly (p < 0.01) higher intensity in Fard than in Khasab, whereas flesh firmness was lower (p < 0.01). Thus, these results suggest that although all three dates serve as a good source of vital nutrients, the Khalas variety, which is considered as premium quality, had significantly higher contents of sugar and selenium and a significantly higher energy value than the other varieties studied.

Arecaceae↗
PubMed2000

Role of organic acids in detoxification of aluminum in higher plants.

Phytotoxicity of aluminum ion (Al3+) is a serious problem limiting crop production on acid soils. Organic acids with Al-chelating ability play an important role in the detoxification of Al both externally and internally. Al is detoxified externally by the secretion of organic acids such as citric, oxalic, and/or malic acids from the roots. The secretion of organic acids is highly specific to Al and the site of secretion is localized to the root apex. The kind of organic acids secreted as well as secretion pattern differ among plant species. There are two patterns of Al-induced secretion of organic acids: In pattern I, there is no discernible delay between the addition of Al and the onset of the release of organic acids. Activation of the anion channel seems to be involved in this pattern; In pattern II, there is a marked lag phase between the addition of Al and the onset of organic acid release. The action of genes related to the metabolism and secretion of organic acids seems to be involved in this pattern. Internal detoxification of Al in Al-accumulating plants is achieved by the formation of Al-organic acid complex. For instance, the complex of Al-citrate (1:1) in hydrangea and Al-oxalate (1:3) in buckwheat has been identified.

Aluminum↗
PubMed1987

[Effect of acid metabolites on the osteoinductive activity of the bone matrix].

The osteoinductive activity of bone matrix demineralized in acid metabolites of glycolysis and Krebs cycle have been studied in rats. The highest osteoinductive effect was reached during the demineralization in oxaloacetic acid, the lowest one--in the malic acid. The regulatory role of glycolysis metabolites and Krebs Cycle in posttraumatic osteogenesis is under discussion.

Animals↗
PubMed1984

[Experiments to replace asparagine in Sauton's medium with organic acids in producing PPD tuberculins].

Studied were some carbonic acids to replace asparagine in Soton's original medium in the production of PPD-tuberculins. Used were the following carbonic acids: (a) dicarboxylic saturated--oxalic, malonic, and amber acid; (b) dicarboxylic unsaturated--maleic and fumaric; and (c) dibasic oxicarbonic acids--malic and tartaric. Each of these acids participated in an equal amount as that of asparagine in replacing it in Soton's medium. Two strains were used in the experiments--AN5 and D4. Tuberculins were obtained through precipitating a filtrated material of cultures killed with trichloracetic acid. The tuberculins produced (bovine and avian PPD types) with the use of the various carbonic acids were tested on sensibilized guinea pigs and chickens parallel to the testing of standard tuberculins. The results obtained with the use of carbonic PPD-tuberculins were almost identical to those obtained with the use of standard PPD-tuberculins. The positive results make it reasonable to believe that some of the carbonic acids mentioned above may well be used in the production of PPD-tuberculins.

Animals↗
PubMed1976

[Resistance to levomycetin and activity of several enzymes in Escherichia coli and the agent of plague].

The authors compared the activity of acetyl-CoA-synthetase and of the enzymes belonging to the group of asparaginic acid in levomycetin sensitive and resistant strains of Y. pestis and E. coli. There were revealed marked differences in the activity of aspartase, fumarase, synthetase and desamidase of L-asparagin, and also of the enzyme activated by acetate in the E. coli strains with plasmide resistance. Transmission of R-factor to the pestis was accompanied by decomposition of L-asparadein, formation of AC-CoA. At the same time transformation of L-asparaginic acid catalyzed by aspartase remained on the same low level in the sensitive pestis cultures and their variants with the R-factor. When the resistance was controlled by chromosomal resistance markers, the activity of the enzymes providing formation of L-asparagic acid, its amide and L-malic acid showed no significant change. In chromosomal type of resistance in the mutants of pestis and E. coli the acetyl-CoA-synthetase reaction was as a rule somewhat increased.

Acetate-CoA Ligase↗
PubMed1986

Malate transport in Schizosaccharomyces pombe.

The transport of malate was studied in a Schizosaccharomyces pombe wild-type strain and in mutant strains unable to utilize malic acid. Two groups of such mutants, i.e., malic enzyme-deficient and malate transport-defective mutants, were differentiated by a 14C-labeled L-malate transport assay and by starch gel electrophoresis followed by activity staining for malic enzyme (malate dehydrogenase [oxaloacetate decarboxylating] [NAD+]; 1.1.1.38) and malate dehydrogenase (1.1.1.37). Transport of malate in S. pombe was constitutive and strongly inhibited by inhibitors of oxidative phosphorylation and of the formulation of proton gradients. Transport was a saturable function of the malate concentration. The apparent Km and Vmax values for transport by the parent were 3.7 mM and 40 nmol/min per mg of protein, respectively, while those of the malic enzyme-deficient mutant were 5.7 mM and 33 nmol/min per mg of protein, respectively. Malate transport was pH and temperature dependent. The specificity of transport was studied with various substrates, including mono- and dicarboxylic acids, and the possibility of a common transport system for dicarboxylic acids is discussed.

Bacterial Proteins↗
PubMed1998

Bioconversion of fumaric acid to succinic acid by recombinant E. coli.

Succinic acid was produced efficiently from fumaric acid by a recombinant E. coli strain DH5 alpha/pGC1002 containing multicopy fumarate reductase genes. The effects of initial fumaric acid and glucose concentration on the production of succinic acid were investigated. Succinic acid reached 41 to over 60 g/L in 48.5 h starting with 50 to 64 g/L fumaric acid. Significant substrate inhibition was observed at initial fumaric acid concentration of 90 g/L. L-Malic acid became the major fermentation product under these conditions. Provision of glucose (5-30 g/L) to the fermentation medium stimulated the initial succinic acid production rate over two folds.

Acetic Acid↗
PubMed2003

Application of conformation design in acyclic stereoselection: total synthesis of borrelidin as the crystalline benzene solvate.

The total synthesis of (-)-borrelidin (treponemycin), a structurally distinct 18-membered macrolide antibiotic, has been achieved. It was isolated as the crystalline benzene solvate, and its structure was confirmed by a single-crystal X-ray analysis. The deoxypropionate subunit consisting of four alternating C-methyl groups with a C(4)-C(10) syn/syn/anti orientation was elaborated by a new method of iterative cuprate additions to acyclic alpha,beta-unsaturated esters relying on two consecutive 1,3-inductions and starting with d-glyceraldehyde as the chiral progenitor. The unique Z/E cyanodiene unit was obtained as a single isomer by application of the Still-Gennari olefination protocol. The gamma-hydroxycyclopentane carboxylic acid subunit was prepared from L-malic acid utilizing a sequential introduction of C-vinyl and C-allyl groups, capitalizing on 1,2-induction in an acyclic alpha,beta-unsaturated ester and carbocyclization by a Grubbs ring closure metathesis reaction. The prevalence of 1,3-syn-disposed deoxypropionate triads in the cuprate additions is rationalized on the basis of minimized syn-pentane interactions in the transition states. A virtual diamond lattice was used as a visual tool to portray the low-energy conformations of the acyclic substrates, and corroborated by (1)H NMR homodecoupling studies.

Crystallography, X-Ray↗
PubMed2000

Plastidic metabolite transporters and their physiological functions in the inducible crassulacean acid metabolism plant Mesembryanthemum crystallinum.

The inducible crassulacean acid metabolism (CAM) plant Mesembryanthemum crystallinum accumulates malic acid during the night and converts it to starch during the day via a pathway that, because it is located in different subcellular compartments, depends on specific metabolite transport across membranes. The chloroplast glucose transporter (pGlcT) and three members of the phosphate translocator (PT) family were isolated. After induction of CAM, transcript amounts of the phosphoenolpyruvate (PEP) phosphate translocator (PPT) and the glucose-6-phosphate (Glc6P) phosphate translocator (GPT) genes were increased drastically, while triose phosphate (TP) phosphate translocator (TPT) and the pGlcT transcripts remained unchanged. PPT- and GPT-specific transcripts and transporter activities exhibited a pronounced diurnal variation, displaying the highest amplitude in the light. pGlcT transcripts were elevated towards the end of the light period and at the beginning of the dark period. These findings, combined with diurnal variations of enzyme activities and metabolite contents, helped to elucidate the roles of the PPT, GPT, TPT and pGlcT in CAM. The main function of the PPT is the daytime export from the stroma of PEP generated by pyruvate orthophosphate:dikinase (PPDK). The increased transport activity of GPT in the light suggests a higher requirement for Glc6P import for starch synthesis rather than starch mobilization. Most likely, Glc6P rather than 3-phosphoglycerate or triose phosphates is the main substrate for daytime starch biosynthesis in M. crystallinum plants in which CAM has been induced (CAM-induced), similar to non-green plastids. In the dark, starch is mobilized both phosphorylytically and amylolytically and the products are exported by the GPT, TPT and pGlcT. The transport activities of all three phosphate translocators and the transcript amounts of the pGlcT adapt to changing transport requirements in order to maintain high metabolic fluxes during the diurnal CAM cycle.

Biological Transport, Active↗