Concentrations Of Benzoate Research Articles

Effect of Glycerol Monolaurate and Sodium Benzoate at Different Concentrations, Temperatures and pH on the Growth of Listeria Monocytogenes

ABSTRACTGlycerol monolaurate and sodium benzoate are used as antimicrobial agents in variety of food. In our study; the effect of glycerol monolaurate and sodium benzoate at different concentrations, temperatures and pH on the growth of Listeria monocytogenes was investigated. During the experiments, Listeria monocytogenes strain 1/2a was used. Triptych soy broth was adjusted to pH 5.0, 5.6, 7.0, and supplemented with 5, 6, 7, 8, 9 mg/ml glycerol monolaurate. Sodium benzoate were added to the broth in rates of 0,5, 1, 1,5, 2, 2.5, 3 mg/ml and then approximately 103 cfu/ml L. monocytogenes was inoculated all broth and incubated at 7, 14, 21, and 35°C. Cultures were measured with spectrophotometer at appropriate time intervals to determine the growth inhibitory effect of all tested conditions. The growth inhibitory effect of different concentrations of glycerol monolaurate and sodium benzoate were determined by calculating generation times.L. monocytogenes was growth in sodium benzoate and glycerol monolaurate free broth controls under all conditions. At 7°C pH 5.6 and pH 5.0, growth of L. monocytogenes was inactivated in the presence of all concentrations of sodium benzoate and glycerol monolaurate. Results indicated that temperature and pH are most important factors influencing the efficiency of sodium benzoate and glycerol monolaurate on growth of L. monocytogenes. Thus, generation time of the organism influenced by temperature, pH, concentrations of sodium benzoate and glycerol monolaurate or their combined interactions.

Ortho pathway of benzoate degradation in Pseudomonas putida: induction of meta pathway at high substrate concentrations

The growth of Pseudomonas putida ATCC 49451 on various concentrations of sodium benzoate was examined under batch cultivation. At low initial concentrations (≤400 mgl −1), cell growth rate was described by the Monod model with parameters of maximum specific growth rate, μ m = 0.66 h −1 and saturation constant, K s = 10 mgl −1. At higher initial concentrations (≥500 mgl −1), product inhibition on specific growth and degradation rates was observed; specific growth rate decreased as sodium benzoate was degraded. A change in degradation pathway was observed with different initial concentrations of sodium benzoate. With initial concentrations up to 200 mgl −1, catechol was oxidized via the ortho ring cleavage with the induction of catechol 1,2-dioxygenase. The ortho pathway metabolites namely, catechol, cis, cis-muconate and muconolactone, were identified using gas chromatography/mass spectrometry (GC/MS) after trimethylsilyl (TMS) derivatization. When higher initial concentrations of sodium benzoate were used (≥300 mgl −1), the culture media showed absorbance at 375 nm (A 375) during the later stage of degradation after approximately 200 mgl −1 of sodium benzoate has been transformed. This was attributed to the accumulation of 2-hydroxymuconic semialdehyde (HMSA), which is an intermediate metabolite of the meta ring fission of catechol. It is concluded that cells grown on high enough concentrations of sodium benzoate simultaneously induced catechol 1,2-dioxygenase and catechol 2,3-dioxygenase, thus activating both the ortho and the meta catechol cleavage pathways. It was further found that catechol, a metabolic intermediate of sodium benzoate, did not effectively support the growth of P. putida when used as a sole substrate. Instead, a dark brown polymerization product was formed. We infer that the induction of the meta pathway is a consequence of the accumulation of 1,2-dihydro-1,2-dihydroxybenzoate (DHB) in the media.

Modeling yeast spoilage in cold-filled ready-to-drink beverages with Saccharomyces cerevisiae, Zygosaccharomyces bailii, and Candida lipolytica.

Mathematical models were developed to predict the probability of yeast spoilage of cold-filled ready-to-drink beverages as a function of beverage formulation. A Box-Behnken experimental design included five variables, each at three levels: pH (2.8, 3.3, and 3.8), titratable acidity (0.20, 0.40, and 0.60%), sugar content (8.0, 12.0, and 16.0 degrees Brix), sodium benzoate concentration (100, 225, and 350 ppm), and potassium sorbate concentration (100, 225, and 350 ppm). Duplicate samples were inoculated with a yeast cocktail (100 microl/50 ml) consisting of equal proportions of Saccharomyces cerevisiae, Zygosaccharomyces bailii, and Candida lipolytica (approximately 5.0 x 10(4) CFU/ml each). The inoculated samples were plated on malt extract agar after 0, 1, 2, 4, 6, and 8 weeks. Logistic regression was used to create the predictive models. The pH and sodium benzoate and potassium sorbate concentrations were found to be significant factors controlling the probability of yeast growth. Interaction terms for pH and each preservative were also significant in the predictive model. Neither the titratable acidity nor the sugar content of the model beverages was a significant predictor of yeast growth in the ranges tested.

Chitosan potentiates the antimicrobial action of sodium benzoate on spoilage yeasts.

The objective of this study was to determine whether low concentrations of chitosan and benzoate in combination could be used to enhance the antimicrobial action of either compound alone against three spoilage yeasts in saline solutions. Saccharomyces exiguus, Saccharomycodes ludwigii and Torulaspora delbrueckii were suspended in 0.05 and 0.005% chitosan glutamate and 0.025% sodium benzoate, alone or in combination, in 0.9% saline solutions at pH 6.2 and 4.5. Survivor curves were constructed from viable counts determined periodically for up to 120 min. Chitosan at 0.005% almost doubled the extent of death caused by 0.025% benzoate alone, from about 1-2 log to about 2-4 log cfu ml(-1), depending on pH and target organism. Chitosan (0.005%) and 0.025% sodium benzoate acted synergistically against spoilage yeasts in saline solutions. These results suggest that the natural compound chitosan may be useful as an adjunct in the potentiation of the biocidal efficacy of antimicrobial compounds such as benzoates.

Safety and efficacy of emamectin benzoate administered in-feed to Atlantic salmon, Salmo salar L., smolts in freshwater, as a preventative treatment against infestations of sea lice, Lepeophtheirus salmonis (Krøyer)

The safety and efficacy of emamectin benzoate, administered in-feed to Atlantic salmon smolts, Salmo salar L., held in freshwater, was evaluated as a preventative treatment against sea lice, Lepeophtheirus salmonis, following transfer of fish to seawater. In the safety study, salmon smolts held in freshwater were fed with diets containing emamectin benzoate at nominal doses of 0 (control), 50 (recommended dose) and 250 (5× recommended dose) μg kg −1 fish day −1 for 7 days (days 0–6). Actual dose rates, based on measured concentrations of emamectin benzoate in feed, differences in fish weight, and feed consumed, were 0, 54, and 272 μg kg −1 day −1, respectively. On day 9, fish were transferred to seawater and observed for 14 days. No differences in feeding response, coordination, behaviour, gross and histological appearance were observed between control fish and those that received 54 μg kg −1 day −1. Among smolts that received 272 μg kg −1 day −1, approximately 50% exhibited darker coloration, and one fish (1%) exhibited uncoordinated swimming behaviour. No pathognomonic signs of emamectin benzoate toxicity were identified. In the efficacy study, smolts held in freshwater were fed an unmedicated ration (control group) or emamectin benzoate at 50 μg kg −1 day −1 (treated group) for 7 days (days 0–6). On day 9, fish were re-distributed to eight seawater tanks, each holding 30 control and 30 treated fish. On days 28, 56, 77 and 109, respectively, control and treated fish in two tanks were challenged with L. salmonis copepodites. When lice in each group reached chalimus stage IV, fish were sampled and the numbers of lice were recorded. Fish challenged at day 109 were sampled for the second time when lice were at the adult stage. Efficacy was calculated as the reduction in the mean number of lice on treated fish relative to the mean on control fish. Treatment with emamectin benzoate resulted in an efficacy of 85.0–99.8% in fish challenged at days 28–77, from the start of treatment, and lice counts were significantly lower ( P<0.001) on treated fish than on controls. When fish challenged at day 109 were sampled at day 128, efficacy was 44.3%, but survival of chalimus to adult lice on treated fish was lower, and at day 159, efficacy had increased to 73%. These results demonstrate that treatment of salmon smolts with emamectin benzoate in freshwater was well tolerated and highly effective in preventing sea lice infestation following transfer of fish to seawater.

Growth rate and growth–no-growth interface of Penicillium brevicompactum as functions of pH and preservative acids

The effects of pH and preservative agents such as sorbic acid (E 200), propionic acid (E 280) and sodium benzoate (E 211), on Penicillium brevicompactum growth or growth–no-growth interfaces were studied. Experiments were carried out on solid media maintained at a water activity of 0·9, and incubated at 20°C. Fungal growth was established by diameter measurements for up to 75 days and kinetics were fitted to Baranyi's primary predictive model. The no-growth phenomena was determined by no visible mycelium development after 75 days. A set of 198 experimental data was generated using two experimental designs. Firstly, pH effect on growth rate was analysed by a secondary predictive model including the inhibitory pH value, pHmin, as a parameter. This pH limit value, which depended on the nature of the preservative agent, was estimated to be 5 in the presence of sorbic acid at maximal authorized values in the European Community (2000 mg l−1). Secondly, sorbic acid and sodium benzoate inhibitory concentrations were evaluated at pH 5, by developing a predictive model taking both growth and growth–no-growth data into account. The sorbic acid had a greater inhibitory effect than sodium benzoate, however the limit value of growth of Penicillium brevicompactum depended on both sorbic and sodium benzoate. Finally, a model built with the laboratory medium data was tested on bakery products made at pH 5, a water activity of 0·9 with various concentrations of sorbic and sodium benzoate, and incubated at 20°C. Results were fairly satisfactory even if wide variability was observed for food products.

Purification and Characterization of a Novel 88 kDa Protein from Serum and Vitreous of Patients with Eales’ Disease

Eales’ disease is a perivasculitis that affects the peripheral retina of young adults and results in recurrent vitreous hemorrhage. Although increased oxidative stress and decreased antioxidant defense have been reported to be associated with Eales’ disease, the exact cause for the disease and its pathogenesis are not known. Here is reported the identification, purification and characterization of a new protein from the serum and vitreous of patients with Eales’ disease. This protein was purified using preparative electrophoresis and HPLC. The purified protein had a retention time of 9.2min in RP HPLC. Its molecular weight as determined by gel permeation chromatography was 88kDa hence, it was termed as 88kDa protein. Alcian blue and Schiffs staining revealed 88kDa protein to be a glycoprotein. Proteins purified from both serum and vitreous exhibited anti lipid peroxidation effect on erythrocyte when added during in vitro assay of thiobarbuteric acid reactive substances (TBARS). In addition to this property the protein also has Fe2+sequestering effect. The anti TBARS activity of 88kDa protein was completely inhibited by 0.1mM concentration of parachlromercuric benzoate (PCMB) and 5,5′ dithiobis(2-nitrobenzoic acid) DTNB. The total thiol content (cysteine) of the purified 88kDa protein was found to be 8% by mass. Eighty eight kDa protein from both the sources namely vitreous and serum are immunologically identical when studied using polyclonal antibodies raised in goat against purified serum protein. The N terminal sequence of 88kDa protein by automated Edman’s degradation chemistry is A D D P N S L S P S A F A E A L A L L R D S X L A R F V. The protein and DNA data base search revealed no match to 88kDa protein and hence this was considered as unique protein. Further knowledge on the in vivo function of 88kDa protein is very important to understand its role in the pathogenesis of Eales’ disease.

Modelling bacterial spoilage in cold-filled ready to drink beverages by Acinetobacter calcoaceticus and Gluconobacter oxydans

Mathematical models were created which predict the growth of spoilage bacteria in response to various preservation systems. A Box-Behnken design included five variables: pH (2.8, 3.3, 3.8), titratable acidity (0.20%, 0.40%, 0.60%), sugar (8.0, 12.0, 16.0 * Brix), sodium benzoate concentration (100, 225, 350 ppm), and potassium sorbate concentration (100, 225, 350 ppm). Duplicate samples were inoculated with a bacterial cocktail (100 microl 50 ml(-1)) consisting of equal proportions of Acinetobacter calcoaceticus and Gluconobacter oxydans (5 x 10(5) cfu ml(-1) each). Bacteria from the inoculated samples were enumerated on malt extract agar at zero, one, two, four, six, and eight weeks. The pH, titratable acidity, sugar content, sodium benzoate, and potassium sorbate levels were all significant factors in predicting the growth of spoilage bacteria. This beverage spoilage model can be used to predict microbial stability in new beverage product development and potentially reduce the cost and time involved in microbial challenge testing.

Characterization of the reaction mechanism for the XL-I form of bovine liver xenobiotic/medium-chain fatty acid:CoA ligase.

The XL-I form of xenobiotic/medium-chain fatty acid:CoA ligase was purified to apparent homogeneity from bovine liver mitochondria and used to determine the reaction mechanism. A tersubstrate kinetic analysis was conducted by varying the concentrations of ATP, benzoate and CoA in turn. Both ATP and benzoate gave parallel double-reciprocal plots against CoA, which indicates a Ping Pong mechanism, with either pyrophosphate or AMP leaving before the binding of CoA. Addition of pyrophosphate to the assays changed the plots from parallel to intersecting; addition of AMP did not. This indicates that pyrophosphate is the product that leaves before binding of CoA. Based on end-product inhibition studies, it was concluded that the reaction follows a Bi Uni Uni Bi Ping Pong mechanism, with ATP binding first, followed in order by benzoate binding, pyrophosphate release, CoA binding, benzoyl-CoA release and AMP release. A similar mechanism was obtained when the ligase was examined with butyrate as substrate. However, butyrate activation was characterized by a much higher affinity for CoA. This is attributed to steric factors resulting from the bulkier nature of the benzoate molecule. Also, with butyrate there is a bivalent cation activation distinct from that associated with binding to ATP. This activation by excess Mg(2+) results in non-linear plots of 1/v against 1/[ATP] for butyrate unless the concentrations of Mg(2+) and ATP are varied together.

Characterization of the reaction mechanism for the XL-I form of bovine liver xenobiotic/medium-chain fatty acid:CoA ligase

The XL-I form of xenobiotic/medium-chain fatty acid:CoA ligase was purified to apparent homogeneity from bovine liver mitochondria and used to determine the reaction mechanism. A tersubstrate kinetic analysis was conducted by varying the concentrations of ATP, benzoate and CoA in turn. Both ATP and benzoate gave parallel double-reciprocal plots against CoA, which indicates a Ping Pong mechanism, with either pyrophosphate or AMP leaving before the binding of CoA. Addition of pyrophosphate to the assays changed the plots from parallel to intersecting; addition of AMP did not. This indicates that pyrophosphate is the product that leaves before binding of CoA. Based on end-product inhibition studies, it was concluded that the reaction follows a Bi Uni Uni Bi Ping Pong mechanism, with ATP binding first, followed in order by benzoate binding, pyrophosphate release, CoA binding, benzoyl-CoA release and AMP release. A similar mechanism was obtained when the ligase was examined with butyrate as substrate. However, butyrate activation was characterized by a much higher affinity for CoA. This is attributed to steric factors resulting from the bulkier nature of the benzoate molecule. Also, with butyrate there is a bivalent cation activation distinct from that associated with binding to ATP. This activation by excess Mg2+ results in non-linear plots of 1/v against 1/[ATP] for butyrate unless the concentrations of Mg2+ and ATP are varied together.

Electric field analysis on the improved skin concentration of benzoate by electroporation

The objective in the present study was to understand the relationship between the increased skin concentration of benzoate as a model drug after topical application of its sodium salt and the electric field intensity produced in the skin barrier, the stratum corneum, by electroporation. A piece of excised abdominal hairless rat skin was set in a Franz type diffusion cell, and 0.5% sodium benzoate and physiological saline were applied to the stratum corneum and dermis sides, respectively. Two needle electrodes made of Ag were connected to an electrical power source, which produced exponentially decaying pulses. The electrodes were placed on the skin surface with a distance of 0.5 cm between both electrodes. After the 4 h passive permeation experiment, an electrical pulse was applied to the rat skin at 300 V every minute for 10 min. The skin was then removed from the diffusion cell, and the amounts of benzoate in different positions of the skin specimen were measured. Field intensity generated in the stratum corneum by electroporation was determined by a finite element method using a computer program. The amounts of benzoate at different sites in the skin were almost proportional to the mean field intensity in the corresponding stratum corneum. These results suggested that the enhancing effect of electroporation can be evaluated by the field intensity more directly than the application voltage.

Alteration of the growth rate and lag time ofLeuconostoc mesenteroides NRRL-B523

Bacterial profile modification is an important enhanced oil recovery technique used to direct injected water into a reservoir's low permeability zone containing trapped crude oil. During water flooding, the use of bacteria to plug the high permeability water zone and divert flow into the oil-bearing low-permeability zone will have a significant economic impact. However, during the field implementation of bacterial profile modification, the rapid growth of bacteria near the injection well bore may hinder the subsequent injection of growth media so that profile modification of the reservoir occurs only in the immediate vicinity of the well bore. By slowing the growth rate and prolonging the lag phase, the onset of pore-space plugging may be delayed and the biologically active zone extended deep into the reservoir. High substrate loading, high pH values, and the addition of the growth inhibitors sodium dodecylsulfate and sodium benzoate have been used in combination to alter the growth characteristics of Leuconostoc mesenteroides NRRL-B523 grown in batch conditions. The highest sucrose concentration used in these studies, 500 g/L, produced lag times 12-fold greater than the slowest lag times achieved at low sucrose concentrations. When L. mesenteroides was grown in media containing 500 g/L sucrose, an alkaline pH value threshold was found above which bacteria did not grow. At this threshold pH value of 8.1, an average lag time of 200 h was observed. Increasing the concentration of sodium benzoate had no effect on lag time, but reduced the growth rate until the threshold concentration of 0.6%, above which bacteria did not grow. Last, it was found that a solution of 0.075 mM sodium dodecylsulfate in media containing 15 g/L sucrose completely inhibited bacterial growth.

Characterization of 3-chlorobenzoate degrading aerobic bacteria isolated under various environmental conditions

The rates of bacterial growth in nature are often restricted by low concentrations of oxygen or carbon substrates. In the present study the metabolic properties of 24 isolates that had been isolated using various concentrations of 3-chlorobenzoate, benzoate and oxygen as well as using continuous culture at high and low growth rates were determined to investigate the effects of these parameters on the metabolism of monoaromatic compounds. Bacteria were enriched from different sampling sites and subsequently isolated. In batch culture this was done both under low oxygen (2% O 2) and air-saturated concentrations. Chemostat enrichments were performed under either oxygen or 3-chlorobenzoate limiting conditions. Bacteria metabolizing aromatics with gentisate or protocatechuate as intermediates (gp bacteria) as well as bacteria metabolizing aromatic compounds via catechols (cat bacteria) were isolated from batch cultures when either benzoate or 3CBA were used as C sources, regardless of the enrichment conditions applied. In contrast, enrichments performed in chemostats at low dilution rates resulted in gp-type organisms only, whereas at high dilution rates cat-type organisms were enriched, irrespective of the oxygen and 3-chlorobenzoate concentration used during enrichment. It is noteworthy that the gp-type of bacteria possessed relatively low μ max values on 3CBA and benzoate along with relatively high substrate and oxygen affinities for these compounds. This is in contrast with cat-type of bacteria, which seemed to be characterized by high maximum specific growth rates on the aromatic substrates and relatively high apparent half saturation constants. In contrast, bacteria degrading chlorobenzoate via gentisate or protocatechuate may possibly be better adapted to conditions leading to growth at reduced rates such as low oxygen and low substrate concentrations.

Characterization of 3-chlorobenzoate degrading aerobic bacteria isolated under various environmental conditions.

The rates of bacterial growth in nature are often restricted by low concentrations of oxygen or carbon substrates. In the present study the metabolic properties of 24 isolates that had been isolated using various concentrations of 3-chlorobenzoate, benzoate and oxygen as well as using continuous culture at high and low growth rates were determined to investigate the effects of these parameters on the metabolism of monoaromatic compounds. Bacteria were enriched from different sampling sites and subsequently isolated. In batch culture this was done both under low oxygen (2% O(2)) and air-saturated concentrations. Chemostat enrichments were performed under either oxygen or 3-chlorobenzoate limiting conditions. Bacteria metabolizing aromatics with gentisate or protocatechuate as intermediates (gp bacteria) as well as bacteria metabolizing aromatic compounds via catechols (cat bacteria) were isolated from batch cultures when either benzoate or 3CBA were used as C sources, regardless of the enrichment conditions applied. In contrast, enrichments performed in chemostats at low dilution rates resulted in gp-type organisms only, whereas at high dilution rates cat-type organisms were enriched, irrespective of the oxygen and 3-chlorobenzoate concentration used during enrichment. It is noteworthy that the gp-type of bacteria possessed relatively low µ(max) values on 3CBA and benzoate along with relatively high substrate and oxygen affinities for these compounds. This is in contrast with cat-type of bacteria, which seemed to be characterized by high maximum specific growth rates on the aromatic substrates and relatively high apparent half saturation constants. In contrast, bacteria degrading chlorobenzoate via gentisate or protocatechuate may possibly be better adapted to conditions leading to growth at reduced rates such as low oxygen and low substrate concentrations.

Separation of amino acids in plant tissue extracts by capillary zone electrophoresis with indirect UV detection using aromatic carboxylates as background electrolytes

Amino acids in extracts of plant tissue were separated and detected by capillary zone electrophoresis (CZE) with indirect UV detection. Various aromatic carboxylates such as salicylate, benzoate, phthalate and trimellitate were investigated as background electrolytes (BGEs). A BGE of benzoate gave the best resolution and detector response. Amino acids were separated at a highly alkaline pH to charge amino acids negatively. Separation was achieved by the co-electroosmotic flow (Co-EOF) by the addition of the cationic surfactant myristyltrimethyl-ammonium bromide (MTAB) to the electrolyte. The condtions affecting the separation of amino acids, including electrolyte pH, concentrations of both benzoate and MTAB, were investigated and optimised. Separation of a mixture of 17 amino acids at pH 11.20 with indirect UV detection at 225 nm was achieved with a BGE of 10 mM benzoate containing 1.0 mM MTAB at pH of 11.20. Detection limits ranged between 10 and 50 μM. The proposed method was demonstrated by the determination of amino acids in extracts of Eucalypt leaves with direct injection of samples.

Electrochemical Studies of the Benzoate Adsorption on Au (111) Electrode

Cyclic voltammetry (CV), differential capacity (DC), and charge densitymeasurements have been employed to study the benzoate (BZ) adsorption at the Au(111)electrode surface. Thermodynamic analysis of charge density (σM) data has beenperformed to describe the properties of the adsorbed benzoate ion. The Gibbsexcess Γ, Gibbs energy of adsorption ΔG, and the number of electrons flowingto the interface per adsorbed benzoate ion at a constant potential (electrosorptionvalency) and at a constant bulk concentration of the benzoate (reciprocal of theEsin—Markov coefficient) have been determined. The results demonstrate thatalthough benzoate adsorption starts at negative charge densities, it takes placepredominantly at a positively charged surface. At the most positive potentials,the surface concentration of benzoate attains a limiting value of about 7.3×10−10mol-cm−2, which is independent of the bulk benzoate concentration. This valueis consistent with packing density corresponding to a closed-packed monolayerof vertically adsorbed benzoate molecules. At negative charge densities, benzoateassumes a flat (π-bonded) surface coordination. The surface coordination ofbenzoate changes, by moving from a negatively to positively charged surface.At the negatively charged surface, the electrosorption bond is quite polar. Thepolarity of the chemisorption bond is significantly reduced due either to a chargetransfer or a screening of the charge on the anion by the charge on the metal.

A non-toxic antifouling compound for marine paints

Laboratory tests with the common barnadeBalanus amphitrite showed narcotic effect on nauplii, cyprids and odults of a solution of sodium benzoate in artificial sea water. This effect was faster as the concentration of sodium benzoate was increased. Field trials confirmed it was successfull in preventing barnade deposition on soluble matrix paints formulated with sodium benzoate as the antifouling agent. These results indicate the potential bio-activity of sodium benzoate on fouling organisms.

FTIR studies of benzoate adsorption on the Au(111) electrode

Abstract Subtractively normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS) has been used to examine (i) the orientation and coordination of benzoate on the Au(111) electrode; (ii) the dependence of the IR band intensity on the surface coverage; and (iii) the chemical stability of benzoate at the Au(111) surface. The results indicate that orientation of adsorbed benzoate changes from a nearly flat co-ordination at a negatively charged surface to a tilted position at positive charge densities. The transition in the orientation of the adsorbed molecule occurs in the vicinity of the potential of zero charge in the solution investigated. The integrated IR band intensities correlate very well with the surface concentration of benzoate obtained from chronocoulometric measurements. An overall agreement between the spectroscopic and electrochemical results is excellent. The spectroscopic data demonstrate that no decomposition or oxidation of benzoate occurred at the Au(111) electrode surface over the potential range investigated.

Electrochemical behaviour of iron in neutral solutions of acetate and benzoate anions

The electrochemical behaviour of iron in pH 6 aqueous solutions of benzoate and acetate anions mixed in varying concentrations and constant ionic strength was investigated. For that purpose cyclic voltammetric experiments were carried out at a disc electrode either static and/or rotating. A high surface coverage is observed in the presence of benzoate anions, thus favouring the establishment of a passive state. The overall process is discussed in terms of a three-dimensional film, the growth mechanism of which is under diffusion and migration control. It was also observed that the addition of chloride ions to the mixed electrolyte solutions containing increasing benzoate concentration shifts the breakdown potential and the repassivation potential toward more positive values.

The role of benzoate in anaerobic degradation of terephthalate.

The effects of acetate, benzoate, and periods without substrate on the anaerobic degradation of terephthalate (1, 4-benzene-dicarboxylate) by a syntrophic methanogenic culture were studied. The culture had been enriched on terephthalate and was capable of benzoate degradation without a lag phase. When incubated with a mixture of benzoate and terephthalate, subsequent degradation with preference for benzoate was observed. Both benzoate and acetate inhibited the anaerobic degradation of terephthalate. The observed inhibition is partially irreversible, resulting in a decrease (or even a complete loss) of the terephthalate-degrading activity after complete degradation of benzoate or acetate. Irreversible inhibition was characteristic for terephthalate degradation only because the inhibition of benzoate degradation by acetate could well be described by reversible noncompetitive product inhibition. Terephthalate degradation was furthermore irreversibly inhibited by periods without substrate of only a few hours. The inhibition of terephthalate degradation due to periods without substrate could be overcome through incubation of the culture with a mixture of benzoate and terephthalate. In this case no influence of a period without substrate was observed. Based on these observations it is postulated that decarboxylation of terephthalate, resulting in the formation of benzoate, is strictly dependent on the concomitant fermentation of benzoate. In the presence of higher concentrations of benzoate, however, benzoate is the favored substrate over terephthalate, and the culture loses its ability to degrade terephthalate. In order to overcome the inhibition of terephthalate degradation by benzoate and acetate, a two-stage reactor system is suggested for the treatment of wastewater generated during terephthalic acid production.