A dual-functional single-atom modified SnS2/CdS S-scheme photocatalyst for synergistic hydrogen production and lactic acid oxidation: A DFT study

The blood of certain species converts glucose to lactic acid but lacks the power of oxidizing either, and of oxygen consumption. The observation by Fürth and Lieben of lactic acid destruction by horse erythrocytes was not confirmed by Warkany; while Koechig in this laboratory using the method described by Ray failed to detect loss of lactate or formation of acetaldehyde. It appears that such “activation” of glucose as occurs in glycolysis does not alone suffice to accomplish the oxidation either of glucose or lactic acid—or an intermediate—by molecular oxygen. The same inference can be drawn from the similar behavior of cancer tissue or muscle extracts, the glycolyzing power of which is little affected by oxygen (Warburg and Meyerhof). Recently Barron and Harrop have shown that the addition of methylene blue to blood undergoing glycolysis causes a marked change in its behavior. There results an increase of O2 consumption and of CO2 production, and a large part of the sugar which disappears fails to appear as lactic acid, thus resembling reactions observed with muscle and other tissues. In the presence of the dye the blood respires with the oxidation, presumably, of either glucose or lactic acid or both. The rate of sugar disappearance is only slightly affected. The dye appears to supply an oxidation catalyst of a sort which is normally absent. We have confirmed the observations of Barron and Harrop cited above and have attempted to decide whether it is the glucose which is oxidized and thus prevented from appearing as lactic acid, or whether lactic acid may be first formed and subsequently oxidized. Our results show that dl-sodium lactate added to washed blood erythrocytes disappears on incubation in air in the presence, but not in the absence of methylene blue.

The rates of formation and oxidation of plasma lactic acid were measured in dogs, either resting quietly or running at 6 km/h on the level, by priming and continuous infusion with uniformly labelled 14C-lactic acid. During running at rates of oxygen consumption almost 5 times the resting value, corresponding to approximately 30% of the maximal effort, the rates of lactic acid formation and disposal were always greater than at rest and doubled on the average. Average plasma lactic acid concentrations during running were greater, equal, or lower than at rest in different dogs. The energy released by formation of the extra lactic acid from glucose during running represented, energetically, less than 0.5% of the extra energy cost of running. Seventy-four percent of the lactate formed was promptly converted to CO2, and about 12% of the respiratory carbon was derived from lactic acid in the running dogs. About 10% of the plasma glucose was derived from lactic acid during both rest and activity. At similar plasma lactate concentrations, running dogs had greater rates of formation of lactic acid than resting animals.

Oxidation of propylene glycol and lactic acid to pyruvic acid in aqueous phase catalyzed by lead-modified palladium-on-carbon and related systems

The promotional dual role of Pd Metallene in ZnCdS-based photocatalytic H2 evolution and lactic acid oxidation.

Four cocoa-specific acetic acid bacterium (AAB) strains, namely, Acetobacter pasteurianus 386B, Acetobacter ghanensis LMG 23848(T), Acetobacter fabarum LMG 24244(T), and Acetobacter senegalensis 108B, were analyzed kinetically and metabolically during monoculture laboratory fermentations. A cocoa pulp simulation medium (CPSM) for AAB, containing ethanol, lactic acid, and mannitol, was used. All AAB strains differed in their ethanol and lactic acid oxidation kinetics, whereby only A. pasteurianus 386B performed a fast oxidation of ethanol and lactic acid into acetic acid and acetoin, respectively. Only A. pasteurianus 386B and A. ghanensis LMG 23848(T) oxidized mannitol into fructose. Coculture fermentations with A. pasteurianus 386B or A. ghanensis LMG 23848(T) and Lactobacillus fermentum 222 in CPSM for lactic acid bacteria (LAB) containing glucose, fructose, and citric acid revealed oxidation of lactic acid produced by the LAB strain into acetic acid and acetoin that was faster in the case of A. pasteurianus 386B. A triculture fermentation with Saccharomyces cerevisiae H5S5K23, L. fermentum 222, and A. pasteurianus 386B, using CPSM for LAB, showed oxidation of ethanol and lactic acid produced by the yeast and LAB strain, respectively, into acetic acid and acetoin. Hence, acetic acid and acetoin are the major end metabolites of cocoa bean fermentation. All data highlight that A. pasteurianus 386B displayed beneficial functional roles to be used as a starter culture, namely, a fast oxidation of ethanol and lactic acid, and that these metabolites play a key role as substrates for A. pasteurianus in its indispensable cross-feeding interactions with yeast and LAB during cocoa bean fermentation.

Effect of Mn(II) and Ce(IV) Ions on the Oxidation of Lactic Acid by Chromic Acid

Photocatalytic hydrogen production is a promising method for solar energy harvesting. To achieve highly efficient photocatalytic reactions, it is necessary to utilize visible light effectively, which constitutes a significant portion of the sunlight spectrum. However, there are only few reports of photocatalytic materials that exceed an external quantum efficiency (EQE) of 50% in photocatalytic hydrogen evolution under visible light. Therefore, to achieve a higher efficiency, here we combined CdS, one of representative visible-light-responsive photocatalysts, with Pt nanoparticles as co-catalysts suitable for hydrogen production, and controlled the morphology of CdS through photoelectrochemical etching. We prepared the CdS-Pt photocatalysts through three-steps: (1) synthesis of highly crystalline CdS in a molten salt, (2) loading Pt co-catalysts onto CdS by photoelectrochemical deposition utilizing surface defects, and (3) partial etching of CdS during photocatalytic hydrogen evolution by using excessive holes.(1) Synthesis of highly crystalline CdS via molten salt treatment: Zincblende CdS particles were prepared from cadmium nitrate and treated further in molten NaCl and CaCl2 to obtain highly crystalline wurtzite CdS (Figure 1a).1 (2) Loading of Pt co-catalysts utilizing surface defects: The prepared wurtzite CdS was irradiated with light (430 nm) in an aqueous solution of lactic acid under a nitrogen atmosphere. In this process, photo-excited electrons are trapped in sulfide ion defects at the CdS surface, while holes are consumed by oxidation of lactic acid. Then, [PtCl6]2- ions were added to the solution in the dark and Pt co-catalysts were deposited onto CdS through reduction reaction of the ions by the trapped electrons (Figure 1b).2 (3) Morphology control of CdS through photoelectrochemical etching: The resulting CdS-Pt was dispersed again in the lactic acid solution and irradiated with light (430 nm) under nitrogen atmosphere. Photo-excited electrons are used for hydrogen evolution through reduction of protons, while holes are consumed by the oxidation of lactic acid and self-oxidation of CdS. In particular, when the light intensity is high, the generation rate of excited carriers as well as the reduction rate of protons exceed the oxidation rate of lactic acid, and partial photoetching of CdS via the self-oxidation occurs significantly. As a result of the photoetching, the surface area of the photocatalyst was increased (Figure 1c). After the photoetching process, we evaluated the photocatalytic activity of the photoetched CdS-Pt for a hydrogen production reaction in a NaOH solution containing 20 vol% 2-propanol, in which high pH suppresses dissolution of cadmium ions and thereby further photoetching. We found that the hydrogen generation rate was improved by ~8 times. The EQE of the hydrogen production reaction using the photoetched CdS-Pt was calculated to be 91%. The specific surface area of CdS-Pt increases and the distance of photogenerated carriers to reach the surface decreases due to the photoetching. These changes are favorable for the photocatalytic reaction and may contribute to the increased activity. If the rate of carrier excitation is too high in comparison with the rate of carrier consumption by redox reactions, EQE should be low. However, the photoetching process decreases both the particle volume and the generation rate of excited carriers, while the reaction sites are increased. These should be responsible for the improved EQE. The present technique, which was developed to optimize the morphology of CdS-Pt photocatalyst under given conditions, would lead to highly efficient photocatalytic water splitting and photoreforming reactions, as well as to mechanism analysis of the efficient photocatalytic reactions.References H. Nagakawa, T. Tatsuma, ACS Appl. Energy Mater., 2022, 5, 1465–14657.H. Nagakawa, T. Tatsuma, J. Phys. Chem. C, 2023, 127, 20337–20343. Figure 1

Article Micellar Effects on the Reactions of Chromium(VI) Oxidation of Lactic Acid and Malic Acid in the Presence and Absence of Picolinic Acid in Aqueous Acid Media was published on October 1, 2006 in the journal BioInorganic Reaction Mechanisms (volume 6, issue 2).

<p>Chemical Kinetics Laboratory. Department of Chemistry, College of Science, M. L. Sukhadia University,<br> Udaipur-313 001, India<br> <em>E-mail</em> : hiranbl @rediffmail.com Fax: 91-294-2471150<br> <em>Manuscript received 28 January 2000, revised 6 January 2004, accepted 20 February 2004</em></p> <p>Oxidation of lactic acid by Cr<sup>VI</sup> under acid conditions is catalyzed by bidentate ligands like α,α'-dipyridyl, 8-hydroxyquinollne,<br> picolinic acid, salicylic acid, salicylamide, 5-sulphosalicylic acid and amino acids like glycine, alanine, aspartic acid and hydroxyproline.<br> The catalysis is a function of [Ligand]/[Cr<sup>VI</sup>] ratio and acidity. In case of amino acids, there is a maxima in rate which depends<br> on nature of amino acid, [Ligandj/[Cr<sup>VI</sup>] ratio and [H<sup>+</sup>]. Mechanism involving catalysis and inhibition has been suggested. Pyruvic<br> acid and acetaldehyde in the ratio of 2 : 1 respectively arc obtained as the oxidation products in both uncatalyzed and catalyzed<br> oxidation. This supports the previously held concept that in oxidation of a-substituted carboxylic acids, Cr<sup>VI</sup> and Cr<sup>v</sup> behave alike<br> in bringing about C-H bond rupture while Cr<sup>IV</sup> is responsible for C-C bond cleavage products.</p>

CdS nanodots adorned (020)-featured WO3·H2O nanoplates heterojunction with augmented photocatalytic hydrogen production under Z-scheme charge transfer mechanism

In part III of this series data were presented for the changes in air following periods of anaerobiosis in the rate of CO2 production of potato tubers and in the contents of sugar, lactic acid and other constituents. Here these experimental data are analyzed and further discussed. The time curve for decrease in the content of lactic acid in air following a period of anaerobiosis appeared to be nearly linear initially with a sharp inflexion as the air value of lactic acid was approached. For a given content of lactic acid the rate of loss of the acid was the more rapid, the shorter the period of anaerobiosis. Preliminary data for the changes in the content of pyruvic and other keto-acids in air following nitrogen were mentioned and the forms of the curves for loss of lactic acid were considered in relation to the system pyruvic acid + Co I. H2 ⇌ L-lactic acid + Co I lactic dehydrogenase The possible influence of changes both in the content of pyruvic acid and in the quotient Co I. H2/Co I on the form of the lactic acid content/time curve was noted. It was provisionally suggested that the effective activity of lactic acid dehydrogenase might decrease progressively in nitrogen and that this loss of activity might not be quickly reversed in air following nitrogen; alternatively in air following nitrogen, owing to the accumulation of reduced compounds during anaerobiosis, the quotient Co i.H2/Co i might for a time be maintained larger the longer the previous period of anaerobiosis. The CO2 production in the after-effect was shown to have a dual origin, being derived partly from lactic acid and partly from sugar. The view was advanced that lactic acid was first oxidized to pyruvic acid, which was then transformed, either in part or completely, into other acids, possibly via the Krebs cycle. The keto-acids of the Krebs cycle may thus be the immediate substrates of the CO2 production which is derived from lactic acid. The quantitative evaluation of the share of the two components, i. e. the non-sugar and the sugar CO2 components, in the total CO2 production, and the elucidation of the fate of the lactic acid presented serious difficulties. The analysis of the CO2 production/sucrose relation during the after-effect in dicated that when lactic acid had decreased to the low level characteristic of aerobic conditions the CO2 production was, for a time which varied in extent in the different experiments, approximately proportional to the sucrose concentration; how ever, in comparison with the values for samples held through out in air, the proportionality factor, i. e. CO2 production/sucrose, was depressed to a greater or lesser extent in different experiments. If it was assumed first that the depression of sugar respiration during the time when lactic acid was disappearing was no greater than after the acid had decreased to the air-level and second that the respiration of sugar continued normally in the after-effect unaffected by the simultaneous oxidation of lactic acid, only a part of the lactic acid loss could be accounted for by CO2 production; it was suggested that the residue of the lactic acid was either in part metabolized to other compounds, e. g. other organic acids, or was in part resynthesized to carbohydrate as in frog’s muscle (Meyerhof 1930). If, however, the respiration of sugar was assumed to be partly suppressed by the increased concentration of pyruvic acid arising from the rapid oxidation of lactic acid, then a greater proportion but not the whole of the lactic acid loss could be accounted for as CO2 production; in this case, in addition to conversion to other organic acids and possibly resynthesis to carbohydrate as already mentioned, a part of the lactic acid would be oxidized in stead of sugar and so spare the normal consumption of sugar in respiration. The results confirm the observations of Singh (1927) on CO2 production in the after-effect and extend them by the information provided by the data for the concomitant changes in the contents of lactic acid and sugar.

Comparative lactic acidosis in fishes following pesticide stress

Recent progress in glycerol oxidation to lactic acid and pyruvic acid with heterogeneous metal catalysts

Spectrophotometric method has been used to characterize water‐soluble colloidal manganese dioxide obtained by the redox reaction between sodium thiosulphate and potassium permanganate in neutral aqueous medium which shows a single peak in the visible region with λmax = 425 nm. The kinetics of the oxidation of lactic acid by colloidal manganese dioxide (oxidant) has been investigated spectrophotometrically under pseudo‐first‐order conditions of excess lactic acid. The rate of the noncatalytic reaction pathway was slow which increased with increasing lactic acid concentration. The reaction was first‐order with respect to [oxidant] as well as [lactic acid]. In presence of manganase(II) and fluoride ions, the noncatalytic path disappeared completely while the oxidation rate of autocatalytic path increased and decreased, respectively with increasing [Mn(II)] and [F−]. A mechanistic scheme in conformity with the observed kinetics has been proposed with the rate‐law: equation image © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 359–366 2004

Screen printed carbon electrode modified with WS2 nanosheet incorporated with cobalt oxide for non-enzymatic detection of lactic acid