Oxidation Of Gluconic Acid Research Articles

Exceptional performance of bimetallic Pt1Cu3/TiO2 nanocatalysts for oxidation of gluconic acid and glucose with O2 to glucaric acid

Catalytic synthesis of glucaric acid by oxidation of gluconic acid/glucose using novel TiO2-supported bimetallic PtCu catalysts and O2 as oxidant is reported, with significantly enhanced activity and selectivity compared to those in previous work. Bimetallic alloy Pt1Cu3 catalysts supported on TiO2 display unusual synergy and exceptional oxidation activity (3543h−1) compared with monometallic Pt and Cu catalysts (13–550h−1), with 46% glucaric acid selectivity at 45°C and 0.1MPa O2. Further, it is shown with the Pt1Cu3 alloy catalyst that glucose may also be directly oxidized to glucaric acid and co-products (tartronic and oxalic acids). The oxidation catalyst reported here provides a green route for making glucaric acid, eliminating conventionally used stoichiometric reagents such as mineral acids and bleach enhancers.

Phosphate-solubilization mechanism and in vitro plant growth promotion activity mediated by Pantoea eucalypti isolated from Lotus tenuis rhizosphere in the Salado River Basin (Argentina)

To isolate and characterize phosphate-solubilizing strains from a constrained environment such as the Salado River Basin and to assess their phosphate-solubilizing mechanisms, to further selection of the most promising strains to inoculate and improve the implantation and persistence of Lotus tenuis in the most important area devoted to meat-cow production in Argentina. Fifty isolates were obtained and through BOX-PCR analysis, 17 non-redundant strains were identified. Subsequently, they were found to be related to Pantoea, Erwinia, Pseudomonas, Rhizobium and Enterobacter genera, via 16S rRNA gene sequence analysis. This was in agreement with the clusters obtained by antibiotic resistance analysis. All isolates were tested for their phosphate-solubilizing activity and selected strains were inoculated onto L. tenuis plants. The most efficient isolate, was identified as Pantoea eucalypti, a novel species in terms of plant growth-promoting rhizobacteria. The isolates obtained in this study showed a significant in vitro plant-growth promoting activity onto Lotus tenuis and the best of them solubilizes phosphate mainly via induction of the metabolism through secretion and oxidation of gluconic acid. The use of these bacteria as bioinoculants, alone or in combination with nitrogen-fixing micro-organisms, could be a sustainable practice to facilitate the nutrient supply to Lotus tenuis plants and preventing negative side-effects such as eutrophication.

Reactivity of ferrate(V) with carboxylic acids: A pre-mix pulse radiolysis study

Rates of reduction of ferrate(VI) to ferrate(V) by a number of organic acid and ester radicals (monocarboxylic acids, dicarboxylic acids, amino acids, malonic acid esters), generated by the pulse radiolysis technique, vary from 10 7–10 9 dm 3 mol -1 s -1. The rate at which these radicals reduce ferrate(VI) depends upon the nature of the substituents at the α-carbon atom and decrease in the order α- C-NH 2>α-C-OH>α-C-H.A similar dependence upon the α-C-groups(s) has been observed for the oxidation of the parent organic acid by ferrate(V), for which the rate constants vary from 10 1-10 6 dm 3 mol -1 s -1. An oxidation mechanism is being proposed in which ferrate(V) oxidizes the carboxylic acid by a two-electron process. The rate of the oxidation process is dependent on the protonation of ferrate(V). For example, in the oxidation of gluconic acid with H 2Fe VO 4 -/HF e VO 4 2-; k 10(H 2Fe VO 4 - + gluconate) = 1.1 × 10 6 dm 3 mol -1 s -1 and k 11(HFe VO 4 2- + gluconate) = 2.0 × 10 5dm 3 mol -1 s -1. The oxidation mechanisms for malate and asparate by OH radicals and ferrate(V) are compared.

Oxidation of D-gluconic acid by chromium(VI) in perchloric acid

The oxidation of gluconic acid by chromium(VI) in perchloric acid has been found to follow the rate law: −d[CrVI]/dt = (k′1 + k′2[GA])[H+]2[CrVI], where k′1 = (7.1 ± 0.2) × 10−4 M−2 s−1 and k′2 = (9.4 ± 0.2) × 10−2 M−3 s−1. This rate law corresponds to the reaction leading to the formation of 2-ketogluconic acid by C—H cleavage when a 20-fold or higher excess of acid over chromium(VI) is employed. Buildup and decay of chromium(V) intermediates accompany the decay of chromium(VI). Chromium(V) rates of decay are similar or slower than those of chromium(VI), as observed by electron paramagnetic resonance (epr) and visible spectrophotometry.

The influence of energy deficiency‐imposing conditions on the capacities ofAcetobacter methanolicus to oxidize glucose and to produce gluconic acid

AbstractThe presence of dinitrophenol (DNP) during the chemostatic growth of Acetobacter methanolicuson glucose led to i) no significant increase in glucose dehydrogenase, ii) a decrease in the capacity to oxidize glucose by about 30%, not depending on the DNP concentration, and iii) a gradual decrease in the capacity to form gluconic acid, depending on the concentration of the uncoupler. Similar effects of DNP on Acetobacter methanolicuswere observed during the gluconic acid formation process. The loss in the capacity to form gluconic acid is indicated by a drop in the ATP concentration of the cells which cannot be counteracted by the ATP syntheses originating from the oxidation of gluconic acid and of glucose. ATP could be necessary for pumping protons out of the cells that were taken up together with gluconic acid and by the effect of DNP.

Continous production of free gluconic acid by Gluconobacter suboxydans IFO 3290 immobilized by adsorption on ceramic honeycomb monolith: effect of reactor configuration on further oxidation of gluconic acid to keto-gluconic acid

Gluconobacter suboxydans IFO 3290 was immobilized by adsorption on ceramic honeycomb monolith, and continuous production of free gluconic acid from 100 g/l glucose was carried out in one- and three-stage monolith reactors. Further oxidation of gluconic acid to keto-gluconic acid by the immobilized cells has been found to be more suppressed in the three-stage monolith reactor. This finding can be explained by the fact that, with the three-stage reactor, the opportunity to oxidize gluconic acid further was decreased because the residence time of the reaction mixture at glucose conversion above the threshold value was shorter.

The oxidation of gluconic acid with platinum on carbon as catalyst

In the oxidation of gluconic acid with platinum on carbon as catalyst, a deactivation of the catalyst takes place due to both chemisorption of oxygen (formation of PtO) and oxidation of the platinum surface (formation of PtO 2). Both types of deactivation can be reversed by temporarily replacing the oxygen flow by a nitrogen flow. Chemisorbed oxygen reacts relatively rapidly with the intermediate product guluronic acid and relatively slowly with gluconic acid and glucaric acid. Consequently, the degree of coverage by chemisorbed oxygen changes in batch experiments due to the change of the concentration of gluconic acid and its reaction products. The deactivation due to the formation of PtO 2 and the oxidation reaction are chemically coupled, and are explained in the same way as in the oxidation of glucose.

Purification and Properties of 5-Ketogluconate Reductase from Gluconobacter liquefaciens

5-Ketogluconate reductase (5KGR) from the cell free extract of Gluconobacter liquefaciens (IFO 12388) was partially purified about 120-fold by a procedure employing ammonium sulfate fractionation, and DEAE-cellulose-, hydroxylapatite- and DEAE-Sephadex A-50-column chromatographies. NADP was specifically required for the oxidative reaction of gluconic acid. The optimum pH for the oxidation of gluconic acid (GA) to 5-ketogluconic acid (5KGA) by the enzyme was 10.0 and for the reduction of 5KGA was 7.5. The optimum temperature of the enzyme was 50°C for both reactions of oxidation and reduction. The enzyme was considerably unstable and lost all of its activity within 3 days. The enzyme activity was strongly inhibited with p-chloromercuribenzoate and mercury ion, but remarkably stimulated by EDTA (1 × 10−3m). Apparent Km values were 1.8 × 10−2m for GA, 0.9 × 10−3m for 5KGA, 1.6 × 10−5 m for NADP, and 1.1 × 10−5 m for NADPH2.

Purification and Properties of 2-Ketogluconate Reductase from Gluconobacter liquefaciens

2-Ketogluconate reductase (2KGR) from the cell free extract of Gluconobacter liquefaciens (IFO 12388) was purified about 1000-fold by a procedure involving ammonium sulfate fractionation and column chromatographies using DEAE-cellulose, hydroxylapatite, and Sephadex gel The purified enzyme gave a single band on polyacrymamide gel electrophoresis. NADP was specifically required for the oxidation reaction of gluconic acid. Using gel filtration a molecular weight of about 110,000 was estimated for the enzyme. The pH optimum for the oxidation of gluconic acid (GA) to 2-ketogluconic acid (2KGA) by the enzyme was 10.5 and for the reduction of 2KGA was 6.5. The optimum temperature of the enzyme was 50 C for both reactions of oxidation and reduction. The enzyme was stable at pH between 5.0 and 11.0 and at temperature under 50°C, The enzyme activity was strongly inhibited with p-chloromercuribenzoate and mercury ions, but remarkably stimulated by manganese ions (1×10−3 m). Km value of the enzyme for GA was 1.3×10™...

Gluconic dehydrogenase of Pseudomonas aeruginosa

1. 1. The purification, isolation and properties of gluconic dehydrogenase from P. aeruginosa 9027 have been described. 2. 2. Pyocyanine has been found to be the most active hydrogen acceptor for the enzyme. 3. 3. The enzyme catalyzes the oxidation of gluconic acid without phosphorylation of the substrate.