Inhibitory Effects Of Organic Acids Research Articles

Inhibitory effect of organic acids on human neutrophil myeloperoxidase’s peroxidation, chlorination, and nitration activities

Abstract Objectives Myeloperoxidase from polymorphonuclear leukocytes is an important enzyme in oxidative metabolism and has a key role in tissue injuries in oxidative stress and inflammatory conditions. Therefore, its inhibitors have become the focus of studies on new drug development in recent years. The aim of the study was to determine the inhibitory effect of organic acids on the peroxidation, chlorination, and nitration activities of myeloperoxidase. Methods Seven organic acids naturally abundant in plants were tested. Different activities of myeloperoxidase were measured in the presence of various amounts of organic acids, and inhibition rates and kinetic parameters were determined for each organic acid separately. Results All the organic acids examined had inhibitory effects on the different activities of myeloperoxidase. Comparison of the IC50 values obtained for peroxidation, chlorination, and nitration activities showed that oxalic acid was the strongest inhibitor of myeloperoxidase activity, while citric acid and succinic acid were the weakest. Conclusions The results suggested that all the organic acids examined are inhibitors of myeloperoxidase. In particular, oxalic acid and fumaric acid are popular candidates for drug development research. More studies are needed to determine the in vivo effects of organic acids and their effects in the treatment of disease.

In Vitro Inhibitory Effects of Organic Acids Identified in Commercial Vinegars on α-Amylase and α-Glucosidase.

The aim of this work was to evaluate the inhibitory activities of organic acids identified from commercial vinegars on α-amylase and α-glucosidase. Six organic acids (acetic, citric, lactic, malic, succinic, and tartaric) were identified in nine commercial vinegars, whose contents varied considerably depending on the raw materials. Most of the fruit vinegars, comprised of various organic acids, were found to be more effective inhibitors against digestive enzymes than grain vinegars containing mainly acetic acid. Citric acid had the lowest IC50 values for α-amylase and α-glucosidase activities 0.64±0.04 μM/mL and 8.95±0.05 μM/mL, respectively, and thus exhibited the strongest antidiabetic effect. Mulberry fruit vinegar containing the highest content of total organic acid (111.02±1.50 mg/mL) showed the strongest digestive enzyme inhibitory impact. The results indicate that vinegars with higher contents of various organic acids hold strong potential against digestive enzymes.

Differential inhibitory effects of organic acids on pear polyphenol oxidase in model systems and pear puree

The inhibitory effects of ascorbic, citric, ferulic and salicylic acid on pear polyphenol oxidase (PPO) were investigated in model and food system. All four organic acids showed strong inhibition effect in model system. However, compared to model system, inhibitory effect of PPO in pear puree was quite different. Ascorbic acid showed a much weaker effect in pear puree compared to the model system. Similarly, ferulic and salicylic acid had limited inhibitory effect in pear puree. Interestingly, the inhibition of PPO activity was not correlated to browning control in pear puree. Ascorbic acid in low concentration was not effective in inhibiting PPO activity in pear puree but exhibited an excellent anti-browning effect. The study indicates that the level of PPO activity is not always a good indicator of susceptibility to browning in foods. Overall, ascorbic acid showed the strongest inhibition of browning and increased the total phenolic content of pear puree.

Management of Potato Post Harvest Tuber Rots by Some Organic Acids and Essential Plant Oils

Dry and white rots incited by Fusarium solani and Sclerotinia sclerotiorum are responsible to cause the major postharvest losses in potato tubers cv. “Spunta” during cold storage. Isolation trials from potato tubers showing rot symptoms collected from local markets yielded forty-one fungal isolates belonging to six genera. The isolated fungi were purified and identified as Fusarium solani (nine isolates), F. semitectum (seven isolates), Sclerotinia sclerotiorum (six isolates), Alternaria sp. (six isolates), F. oxysporum, (five isolates), Rhizoctonia solani (three isolates), and Penicillium sp. (two isolates). Pathogenicity tests showed that F. solani and S. sclerotiorum were the most pathogenic fungi. The inhibitory effect of organic acids (boric, oxalic and salicylic acids) on the linear growth of F. solani and S. sclerotiorum in vitro showed that the tested organic acids resulted in different degrees of inhibition to the mycelial growth of the two tested fungi compared with control treatment. This inhibition was gradually increased by increasing the concentration of the tested organic acids. In addition, oxalic acid resulted in 100% inhibition to the mycelial growth of the two tested pathogens at 0.4 % concentration. The other organic acids gave intermediate inhibition. The effect of camphor oil (Eucalyptus glabulus), black seed (Nigella sativa), garlic and spearmint oils against Fusarium solani and Sclerotinia sclerotiorum, in vitro and in vivo on tubers during cold storage was determined. Fusarium solani, F. semitectum and Sclerotinia sclerotiorum were completely inhibited by the application of spearmint oil concentrations at 0.3 and 0.4%, in vitro. In vivo results showed also that Nigella sativa preparation was the most effective as it completely suppressed disease severity% caused by Fusarium solani and Sclerotinia sclerotiorum (0.0%) followed by Camphor oil during cold storage. Essential oils maintained highest tubers quality sprouting and reduced weight losses. Generally, treatment with both organic acids and essential plant oils gave effective control for the two pathogens and reduced the loss in fresh weight of potato tubers in addition to reducing the sprout of the tubers during cold storage at 13°C for two months.

Inhibitory Effects of Organic Acids against Pectinolytic Yeasts Isolated from Decayed Citrus

Inhibitory Effects of Organic Acids against Pectinolytic Yeasts Isolated from Decayed Citrus

Enrichment and isolation of acidophilic sulfate‐reducing bacteria from Tinto River sediments

Although some acidophilic and alkaliphilic species have been described recently, most of the known sulfate-reducing bacteria (SRB) grow optimally at neutral pH. In this study, sulfate reduction was studied with sediment samples from the extremely acidic Tinto River basin. Stable enrichments of SRB were obtained at pH 4 with glycerol, methanol and hydrogen; at pH 4.5 with lactate and at pH 5.5 with succinate as substrates. Inhibition of sulfate reduction by organic acids below their pKa was observed. Cloning and sequencing of 16S rRNA gene showed that fermentative bacteria (Paludibacter spp., Oscillibacter spp.) and SRB (Thermodesulfobium spp., Desulfosporosinus spp., Desulfitobacterium spp., Desulfotomaculum spp.) were co-enriched. By repeated serial dilutions and streaking on agar plates, four strains of SRB belonging to the Firmicutes phylum were obtained. Two of them show 96% 16S rRNA gene sequence similarity with Desulfosporosinus acidophilus, and a third one with Desulfosporosinus orientis. Another isolate has just 93% rRNA gene sequence similarity with the Desulfosporosinus/Desulfitobacterium cluster and might represent a novel species within a novel genus. One of the Desulfosporosinus strains was further investigated showing maximum growth at pH 5.5, and a pH-dependent inhibitory effect of organic acids and sulfide.

Growth inhibition of Cronobacter spp. strains in reconstituted powdered infant formula acidified with organic acids supported by natural stomach acidity

Cronobacter is associated with outbreaks of rare, but life-threatening cases of meningitis, necrotizing enterocolitis, and sepsis in newborns. This study was conducted to determine the effect of organic acids on growth of Cronobacter in laboratory medium and reconstituted powdered infant formula (PIF) as well as the bacteriostatic effect of slightly acidified infant formula when combined with neonatal gastric acidity. Inhibitory effect of seven organic acids on four acid sensitive Cronobacter strains was determined in laboratory medium with broth dilution method at pH 5.0, 5.5 and 6.0. Acetic, butyric and propionic acids were most inhibitive against Cronobacter in the laboratory medium. The killing effect of these three acids was partially buffered in reconstituted PIF. Under neonatal gastric acid condition of pH 5.0, the slightly acidified formula which did not exert inhibition effect solely reduced significantly the Cronobacter populations. A synergistic effect of formula moderately acidified with organic acid combined with the physiological infant gastric acid was visible in preventing the rapid growth of Cronobacter in neonatal stomach. The study contributed to a better understanding of the inhibitory effect of organic acids on Cronobacter growth in different matrixes and provided new ideas in terms of controlling bacteria colonization and translocation by acidified formula.

Effect of organic acids on the growth and lipid accumulation of oleaginous yeast Trichosporon fermentans.

BackgroundMicrobial lipids have drawn increasing attention in recent years as promising raw materials for biodiesel production, and the use of lignocellulosic hydrolysates as carbon sources seems to be a feasible strategy for cost-effective lipid fermentation with oleaginous microorganisms on a large scale. During the hydrolysis of lignocellulosic materials with dilute acid, however, various kinds of inhibitors, especially large amounts of organic acids, will be produced, which substantially decrease the fermentability of lignocellulosic hydrolysates. To overcome the inhibitory effects of organic acids, it is critical to understand their impact on the growth and lipid accumulation of oleaginous microorganisms.ResultsIn our present work, we investigated for the first time the effect of ten representative organic acids in lignocellulosic hydrolysates on the growth and lipid accumulation of oleaginous yeast Trichosporon fermentans cells. In contrast to previous reports, we found that the toxicity of the organic acids to the cells was not directly related to their hydrophobicity. It is worth noting that most organic acids tested were less toxic than aldehydes to the cells, and some could even stimulate the growth and lipid accumulation at a low concentration. Unlike aldehydes, most binary combinations of organic acids exerted no synergistic inhibitory effects on lipid production. The presence of organic acids decelerated the consumption of glucose, whereas it influenced the utilization of xylose in a different and complicated way. In addition, all the organic acids tested, except furoic acid, inhibited the malic activity of T. fermentans. Furthermore, the inhibition of organic acids on cell growth was dependent more on inoculum size, temperature and initial pH than on lipid content.ConclusionsThis work provides some meaningful information about the effect of organic acid in lignocellulosic hydrolysates on the lipid production of oleaginous yeast, which is helpful for optimization of biomass hydrolysis processes, detoxified pretreatment of hydrolysates and lipid production using lignocellulosic materials.

Inhibitory effects of organic acids combined with modified atmosphere packaging on foodborne pathogens on cabbage

Inhibitory effects of organic acids combined with modified atmosphere packaging (MAP) on foodborne pathogens, including Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes, on cabbage were evaluated. The cabbage samples were inoculated with cocktails containing each of the three stains, treated with three different organic acids (acetic, lactic, and malic acids) for 10 min at room temperature, and then dried. Populations of E. coli O157:H7, S. Typhimurium, and L. monocytogenes on cabbage were significantly reduced by treatment with 2% acetic, 1% lactic, and 2% malic acids, and their reduction levels were 1.9, 3.3, and 2.6 log10 CFU/g, respectively. Cabbage samples were packaged using four different methods (air, vacuum, N2 gas, and CO2 gas) following treatment with distilled water or 2% lactic acid for 10 min at room temperature and then stored at 10°C. Initial populations of E. coli O157:H7, S. Typhimurium, and L. monocytogenes on cabbage were approximately 6.2, 6.7, and 5.1 log10 CFU/g, respectively, and treatment with 2% lactic acid for 10 min reduced the three pathogens by 3.1, 3.3, and 2.4 log10 CFU/g, respectively. As a result, inhibitory effects of the pathogens were significantly reduced by 2% lactic acid than when using distilled water. MAP was effective in maintaining reduced levels of pathogens during storage following the treatments. However, no significant differences in the levels of pathogens were observed among the samples packaged under four different gas conditions.

Inhibitory effect of organic acids on arcobacters in culture and their use for control of Arcobacter butzleri on chicken skin

The inhibitory effects of 17 organic acids (C2–C16 fatty acids, sorbic, benzoic, phenylacetic, fumaric, succinic, lactic, malic and citric) on Arcobacter butzleri, Arcobacter cryaerophilus and Arcobacter skirrowii were investigated by determining their IC50 values, defined as the concentration of acid at which the target DNA sequence was expressed at 50% of the positive control level in cultures incubated at 30°C for 24h. DNA was analysed by real-time PCR. The Arcobacter strains tested were inhibited by all the organic acids, with the sensitivities in the order A. skirrowii > A. cryaerophilus > A. butzleri. Eight acids with IC50 values of <1mg/mL against A. butzleri were tested for their effects on A. butzleri inoculated on chicken carcasses at a concentration of 5 log CFU/g of skin. Inoculated halved carcasses were immersed in solutions of the acids at 5mg/mL for 1min. Samples of skin were collected from carcass halves after storage at 4°C for 0, 1, 2 or 3days for enumeration of arcobacters on Muller–Hinton agar. All eight tested acids suppressed bacterial proliferation. The highest inhibitory activities were observed for benzoic, citric, malic and sorbic acids. Subsequent sensory analysis revealed benzoic acid to be the most suitable organic acid for chicken skin treatment.

Inhibitory Effects of Organic Acids on Bacteria Growth During Food Waste Composting

During the process of food waste composting, organic acids are generated from microbial breakdown of easily degradable substrates. These organic acids could inhibit microbial activities and sequentially reduce the decomposition efficiency. Considerable relationships among pH, organic-acid concentration and microbial activity were observed in this study. In order to systematically investigate inhibitory effects of four organic acids on composting bacteria, multivariate experimental designs were implemented in day 5 and day 9 during the initial stage of composting. Butyric and propionic acids had significant inhibitory effects on the growth of thermophilic bacteria on day 5. The inhibitory effects of organic acids on composting bacteria became significantly milder on day 9. The effects of different pH control amendments to mitigate microbial inhibition were also preliminarily examined. The treatment of NaAc resulted in the largest population of thermophilic bacteria.

Inhibitory effect of organic acids against Enterobacter sakazakii in laboratory media and liquid foods

Enterobacter sakazakii is an emerging foodborne pathogen that causes neonatal meningitis and sepsis, with mortality rates of 40–80%. This study was conducted to determine the effect of organic acids on inhibiting the survival and the growth of E. sakazakii in laboratory media and several liquid foods. Inhibitory effects and the minimum inhibitory concentration (MIC) of nine acids (hydrochloric, lactic, malic, formic, phosphoric, propionic, citric, tartaric, and acetic acid) against E. sakazakii were determined by the agar disc diffusion test and broth dilution methods. Out of nine acids tested, five acids (malic, formic, propionic, citric, and acetic acid) showed antibacterial activity against one or more E. sakazakii stains. And, propionic and acetic acid were found to be the most effective with the lowest MIC values of 16–31 and 31–63 mM against E. sakazakii, respectively. Therefore, these two acids were selected for further testing in liquid foods ( Sun-Sik, baby food, grape juice and apple juice). Regarding foods tested, grape juice itself has an inhibitory effect and reduced or maintained levels of E. sakazakii during storage. However, 10 mM of propionic and acetic acid in Sun-Sik and apple juice, and 100 mM of propionic and acetic acid in baby foods were necessary to eliminate E. sakazakii in each food type, respectively. These results suggest that organic acids such as propionic and acetic acid may possibly be used as preservatives to inhibit E. sakazakii in liquid foods.

Session IV: Immunology of Mucosal Infections: IV.1–IV.16

Cronobacter is associated with outbreaks of rare, but life-threatening cases of meningitis, necrotizing enterocolitis, and sepsis in newborns. This study was conducted to determine the effect of organic acids on growth of Cronobacter in laboratory medium and reconstituted powdered infant formula (PIF) as well as the bacteriostatic effect of slightly acidified infant formula when combined with neonatal gastric acidity. Inhibitory effect of seven organic acids on four acid sensitive Cronobacter strains was determined in laboratory medium with broth dilution method at pH 5.0, 5.5 and 6.0. Acetic, butyric and propionic acids were most inhibitive against Cronobacter in the laboratory medium. The killing effect of these three acids was partially buffered in reconstituted PIF. Under neonatal gastric acid condition of pH 5.0, the slightly acidified formula which did not exert inhibition effect solely reduced significantly the Cronobacter populations. A synergistic effect of formula moderately acidified with organic acid combined with the physiological infant gastric acid was visible in preventing the rapid growth of Cronobacter in neonatal stomach. The study contributed to a better understanding of the inhibitory effect of organic acids on Cronobacter growth in different matrixes and provided new ideas in terms of controlling bacteria colonization and translocation by acidified formula.

Modeling the inhibitory effects of organic acids on bacteria

The inhibitory effect of acids on microbial growth has long been used to preserve foods from spoilage. While much of the effect can be accounted for by pH, it is well known that different organic acids vary considerably in their inhibitory effects. Because organic acids are not members of a homologous series, but vary in the numbers of carboxy groups, hydroxy groups and carbon–carbon double bonds in the molecule, it has typically not been possible to predict the magnitude, or in some cases even the direction, of the change in inhibitory effect upon substituting one acid for another or to predict the net result in food systems containing more than one acid. The objective of this investigation was to attempt to construct a mathematical model that would enable such prediction as a function of the physical and chemical properties of organic acids. Principal Components Analysis (PCA) was applied to 11 properties for each of 17 acids commonly found in food systems; this resulted in four significant principal components (PCs), presumably representing fundamental properties of the acids and indicating each acid’s location along each of these four scales. These properties correspond to polar groups, the number of double bonds, molecular size, and solubility in non-polar solvents. Minimum inhibitory concentrations (MICs) for each of eight acids for six test microorganisms were determined at pH 5.25. The MICs for each organism were modeled as a function of the four PCs using partial least squares (PLS) regression. This produced models with high correlations for five of the bacteria ( R 2=0.856, 0.941, 0.968, 0.968 and 0.970) and one with a slightly lower value ( R 2=0.785). Acid susceptible organisms ( Bacillus cereus, Bacillus subtilis, and Alicyclobacillus) exhibited a similar response pattern. There appeared to be two separate response patterns for acid resistant organisms; one was exhibited by the two lactobacilli studied and the other by E. coli. Predicting the inhibitory effects of the organic acids as a function of their chemical and physical properties is clearly possible.

A non-passive mechanism of butyrate excretion operates during acidogenic fermentation of methanol by Eubacterium limosum

The inhibitory effects of organic acids produced as fermentation end-products during methylotrophic growth of the acidogenic anaerobe, Eubacterium limosum have been investigated. Precise quantification of the intracellular concentrations of acetate and butyrate, together with delta pH measurements indicate that butyrate efflux cannot be explained by a process of passive diffusion. Intracellular concentrations of butyrate were significantly lower than those of the culture broth. It is argued that growth inhibition by butyrate is due to energetic limitations resulting from the energy drain associated with this non-passive efflux mechanism.

Liquid Phase Oxidation of Xylenes and Toluic Acids with Oxygen, and Inhibitory Effect of Organic Acids on the Oxidation

Reactivities of xylenes in the liquid phase air oxidation at 135°c with cobalt naphthenate catalyst was in order of o->m-≅p-xylene. The velocity of oxidation with cobalt bromide catalyst without solvent in a stationary chainpropagation period was in the order of o-<in-≅p-xylene. The presence of bromine in cobalt catalyst increased the oxidation velocity in the propagation period (with the exception of o-xylene, no solvent system in which the oxidation was decreased). The ratio of the reaction velocity coefficient, k2/k1, in the twostep oxidation of xylenes toluic acids benzenedicaroxylic acids was not much dependent on the kind of xylenes in case of using cobalt naphthenate catalyst. The ratio k2/k1 became smaller with cobalt bromide catalyst than with cobalt naphthenate catalyst. In the liquid phase oxidation of toluic acids at 150°c to benzenedicarboxylic acids, it was found that the reaction was proceeded smoothly in case of m-or p-toluic acids but not in case of o-toluic acid. This may be attributed mainly to inactivation of catalyst by the o-phthalic acid. This kind of inactivation is found commonly in organic acids having a large dissociation constant and was found in case of oxidation of easily oxidizable xylenes too, though the tendency is smoll.