Batch Fermentation Model of Propionic Acid Production by Propionibacterium acidipropionici in Different Carbon Sources

Propionic acid (PA) is widely used as additive in animal feed and also in the manufacturing of cellulose-based plastics, herbicides, and perfumes. Salts of propionic acid are used as preservative in food. PA is mainly produced by chemical synthesis. Nowadays, PA production by fermentation of low-cost industrial wastes or renewable sources has been an interesting alternative. In the present investigation, PA production by Propionibacterium acidipropionici ATCC 4965 was studied using a basal medium with sugarcane molasses (BMSM), glycerol or lactate (BML) in small batch fermentation at 30 and 36 degrees C. Bacterial growth was carried out under low dissolved oxygen concentration and without pH control. Results indicated that P. acidipropionici produced more biomass in BMSM than in other media at 30 degrees C (7.55 g l(-1)) as well as at 36 degrees C (3.71 g l(-1)). PA and biomass production were higher at 30 degrees C than at 36 degrees C in all cases studied. The best productivity was obtained by using BML (0.113 g l(-1) h(-1)), although the yielding of this metabolite was higher when using glycerol as carbon source (0.724 g g(-1)) because there was no detection of acetic acid. By the way, when using the other two carbon sources, acetic acid emerged as an undesirable by-product for further PA purification.     

Immobilisation of Clostridium spp. for production of solvents and organic acids

This review summarises the high potential of immobilised cells systems for the fermentative production of compounds, mainly produced by representatives of the Clostridium genus. Microorganisms of Clostridium species are recognised as good producers of a wide range of chemicals in almost every sector of industry. The combination of this microorganism with its immobilisation opens up new possibilities and renders the fermentation process more sophisticated than in a free-cell system. This review provides a comprehensive summary of techniques used in immobilisation of Clostridium species with regard to specific products and types of fermentation. In addition, comparisons of particular types of immobilisation techniques used in fermentation processes are summarised by specific products.     

N-Methylation and N,N-dimethylation of amino acids. An artifact production in the analysis of organic acids using diazomethane as derivatizing agent

In the fractions of the methyl esters of urinary organic acids seventeen N-methylated or N,N-dimethylated amino acid methyl esters are identified by gas chromatography-mass spectrometry. It is shown for twelve amino acids that their amino group reacts with diazomethane to form these derivatives. Using deuterated reagents, in particular deuterated diazomethane, in the sample preparation procedure during the organic acid analysis, it is shown that the N-methylated and N,N-dimethylated amino acids are artifacts from diazomethane and are not biochemical N-methylation products.     

Fermentation kinetics of ethanol production from glucose and xylose by recombinant Saccharomyces 1400(pLNH33)

Fermentation kinetics of ethanol production from glucose, xylose, and their mixtures using a recombinant Saccharomyces 1400 (pLNH33) are reported. Single-substrate kinetics indicate that the specific growth rate of the yeast and the specific ethanol productivity on glucose as the substrate was greater than on xylose as a substrate. Ethanol yields from glucose and xylose fermentation were typically 95 and 80% of the theoretical yield, respectively. The effect of ethanol inhibition is more pronounced for xylose fermentation than for glucose fermentation. Studies on glucose-xylose mixtures indicate that the recombinant yeast co-ferments glucose and xylose. Fermentation of a 52.8 g/L glucose and 56.3 g/L xylose mixture gave an ethanol concentration of 47.9 g/L after 36 h. Based on a theoretical yield of 0.51 g ethanol/g sugars, the ethanol yield from this experiment (for data up to 24 h) was calculated to be 0.46 g ethanol/g sugar or 90% of the theoretical yield. The specific growth rate of the yeast on glucose-xylose mixtures was found to lie between the specific growth rate on glucose and the specific growth rate on xylose. Kinetic studies were used to develop a fermentation model incorporating the effects of substrate inhibition, product inhibition, and inoculum size. Good agreements were obtained between model predictions and experimental data from batch fermentation of glucose, xylose, and their mixtures.     

Paper chromatography of fatty acids and halogenated organic acids

A paper chromatographic method is described for the identification of the volatile fatty acids and some of their bromo- and iodo-derivatives. Some new spraying reagents are suggested which enable the different classes of acids to be detected in presence of one another.     

Carbon dioxide production in the oxidation of organic acids by Cerium(IV) under aerobic and anaerobic conditions

The stoichiometry of CO₂ production during the ceric oxidation of various organic acids is measured under conditions with organic acid excess. Measurements utilize a photometric methodology. For anaerobic conditions stoichiometries [CO₂]_produced:[Ce(IV)]_reduced of about 0 (malonic acid), 0.5 (e.g., glyoxylic acid), and 1.0 (oxalic acid) are found. Oxalic acid showed an oxygen-induced decrease of CO₂ production, while other compounds such as malonic acid increased the amount of produced CO₂ or showed no changes (e.g., tartronic acid). In the case of mesoxalic acid the stoichiometry is increased from about 0.5 to 2.0 due to the presence of molecular oxygen. The results are discussed on the basis of simple reaction mechanisms demonstrating that useful information on reaction pathways and intermediates can be extracted from these simple measurements. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 899–902, 1998     

Bond energies in polyunsaturated acids and kinetics of co-oxidation of protiated and deuterated acids

A computational program specially designed to analyze co-oxidation of substances in mixtures is suggested. The rigorous kinetic scheme of 32 reactions describing co-oxidation of isotope differing polyunsaturated fatty acids was computed to enlighten experimentally detected enormously large H/D isotope effects. The latter were shown to depend on the kinetic chain length and exhibit two extreme regimes of short and long chains which characterize isotope effects on the initiation and propagation chain reactions of hydrogen (deuterium) atom abstraction. No protective effect of deuterated polyunsaturated acids on the oxidation of protiated acids was detected. Protective effect of the deuterated compounds on the biologically important processes seems to be induced by the low yield of products formed in the chain termination reactions due to the low rate of initiation by deuterated compounds.     

Comparison of ion-pair chromatography and capillary zone electrophoresis for the assay of organic acids as markers of abnormal metabolism

The abnormal organic acids in urine are closely related with physiological metabolism. To determinate the low-molecular-mass metabolites in human biological fluids, although there were some previous reports by both of capillary electrophoresis and ion-exchange high-performance liquid chromatography, but it was rarely found by reverse phase of liquid chromatography using ion pair reagent. The objective of this study was aimed to suggest and compare two methods, an additional chromatographic method-ion-pair chromatography (IPC) and a sharp capillary zone electrophoresis (CZE), to determinate organic acids, acting as the abnormal metabolic markers, namely uric acid, orotic acid, pyruvic acid, alpha-ketoglutaric acid, fumaric acid, and hippuric acid. The proposed method of IPC possessed both the extreme stability for column and the good results of reproducibility, linearity and detection limit. The optimum mobile phase was 22% methanol and 10 mM tetra-n-butyl ammonium hydrogen sulfate (pH 4) by gradient elution. As well as the optimum condition of CZE was 5% acetonitrile and 0.5 mM CTAB in phosphate buffer. From the results, CZE showed better recovery and sharp lucid electropherogram. Finally, the two proposed analytical methods were applied to assay human urine with direct and spiked analysis. CZE showed good potency to overcome the sample-to sample variation with standard deviation less than 10%. By comparison results of urinary spiked analysis between IPC and CZE by statistical paired t-test, the results were evaluated no significant difference under P < 0.05. The quantitative linearity of both methods was fitted in application of clinical biological analysis even with 50-fold dilution.     

Cation exchange kinetics of pyridinecarboxylic acids

The sorption—desorption kinetics of nicotinic and isonicotinic acids on strong acid cationites (sulfocationite CU-2-8, sulfonated polycalixarene) were considered. The rate of the processes, following both the cation exchange mechanism H⁺ ? Cat⁺ and the ion exchange mechanism accompanied by the chemical reaction of protonation of pyridinecarboxylic acid zwitterions, is determined by a slow diffusion of components in the polymeric phase. The interdiffusion coefficient in sulfocationite CU-2-8 for the process H⁺ ? Cat⁺ was equal to ~1?10^–11 m² s^–1, in sulfonated polycalixarene the corresponding value was in the range of (1—4)?10^–12 m² s^–1.     

Analytical aspects of organic acids

Summary Phenyl acetic acid has been found to be a selective reagent for the estimation of zirconium. The acid gives a white crystalline precipitate which is quantitative between pH values of 3.00 to 5.40. As the composition of the precipitate varies somewhat, direct weighing is not possible and the compound is ignited to the oxide. The ions Be²⁺, Ca²⁺, Sr²⁺, Zn²⁺, Hg²⁺, Pb²⁺, Mg²⁺, Ni²⁺, and Co²⁺ do not interfere, whereas the ions Fe³⁺, UO₂ ²⁺, Cr³⁺, Ba²⁺, Au⁺, Al³⁺, V₂O₄ ²⁺, Ti⁴⁺, Sn²⁺, and Ba²⁺ cause interferences in the estimation.

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Zusammenfassung Zur gravimetrischen Bestimmung von Zirkonium wird Phenylessigsäure empfohlen. Die weiße, kristalline Fällung ist im pH-Bereich 3,00–5,40 quantitativ. Infolge schwankender Zusammensetzung des Niederschlages ist eine direkte Wägung nicht möglich; er wird daher zum Oxid verglüht. Folgende Ionen stören nicht: Be²⁺, Ca²⁺, Sr²⁺, Zn²⁺, Hg²⁺, Pb²⁺, Mg²⁺, Ni²⁺ und Co²⁺; dagegen verursachen Fe³⁺, UO₂ ²⁺, Cr³⁺, Ba²⁺, Au⁺, Al³⁺, V₂O₄ ²⁺, Ti⁴⁺, Sn²⁺ und Ba²⁺ Störungen bei der Bestim mung.

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Part VI: See Z. analyt. Chem. 175, 29 (1960).     

Decay kinetics of the triplet and anthrasemiquinone radicals in aqueous organic media

Electron transfer involving triplet molecules of anthraquinone sulfonates has been studied by flash photolysis. It was revealed that semiquinone radicals were formed in one-electron oxidation of carbonate anions. Absorption spectra and the kinetics of decay transients in aqueous and aqueous-alcoholic solutions have been studied.     

Basic profiles of organic acids in urine

Altogether 143 of the organic acids regularly occurring in urine of healthy individuals are identified as methyl esters by gas chromatography-mass spectrometry with respect to their complete chemical structures. They are classified as dicarboxylic acids, oxocarboxylic acids, hydroxycarboxylic acids, aromatic acids, furancarboxylic acids, nitrogen-containing acids and acid conjugates. By pre-fractionating the complex mixture of the total organic acids, peak overlap is minimized, and substances in low concentrations can also be detected and identified. The qualitative patterns of the urinary organic acids in the fractions are constant and reproducible, and in many cases a reliable identification of organic acids is possible by gas chromatography alone, using methylene units and separation on OV-1701 capillary columns.     

Ischemic change of organic acids in kidney

Organic acids in rabbit renal tissue biopsy were analyzed by capillary column gas chromatography--mas s spectrometry. The change of these organic acids under ischemic conditions was determined over 60 min after clamping the renal artery and vein. The results showed that lactic acid, glycolic acid, 2-hydroxybutyric acid, 3-hydroxypropionic acid, 2-methyl-glyceric acid, glyceric acid and malic acid increased at 4 and 6 min after clamping, but then decreased at 15 min. Glycerol increased 2 min after clamping and then decreased. However, 3-deoxyaldonic acids of 3-deoxytetronic acid, 3-deoxy-2-C-hydroxymethyltetronic acid and 3-deoxypentonic acid decreased in the renal tissue biopsy from 2 min after clamping.     

Interaction kinetics of peroxides and organic sulphides in atactic polypropylene

Kinetics of the reactions between benzoyl peroxide and sulphides (dilaurylthyodipropionate and dibenzyl sulphide), of the reaction between diphenylethyl hydroperoxide and dibenzylsulphide in atactic polypropylene and of the reaction of benzoyl peroxide with dibenzyl sulphide in polyisobutylene have been studied. The stoichiometry of the reactions was determined and the dependence of the rate constants on the initial concentration of reactant was established. At low reactant concentrations, the rate constants decrease and at high concentration increase with increasing concentration. In model low-molecular-weight hydrocarbon, the reaction rate constants do not change with reactant concentrations. The reaction mechanism is discussed. It is based on specific features of the dissolution of low-molecular additives in polymer.     

Determination of organic acids and ketones in contaminated soils

Hydrocarbons and metabolites from biodegradation in soil have been isolated and separated using Soxhlet extraction, with n-heptane and dichloromethane, combined with solid-phase extraction on silica gel and basic aluminum oxide using n-pentane, dichloromethane, methanol, and sulfuric acid – methanol as eluents. This procedure can be used for determination of metabolites both in laboratory-prepared soil samples containing mineral oils and in actual contaminated soil. After microbiological degradation, organic acids and ketones which were not original components of the diesel fuel and lubricating oil contaminating the soil samples were identified using capillary gas chromatography – mass spectrometry in batch-soil experiments. Predominantly alicyclic and branched-chain aliphatic organic acids and diacids, and aromatic ketones, were found to be formed after a few weeks degradation.     

Photochemistry and kinetics of single organic nanoparticles in the presence of charge carriers

This paper describes a preliminary experimental study on charge injection in MEH-PPV polymer nanoparticles incorporated in an OLED type device. The nanoparticles have been investigated with single molecule fluorescence spectroscopy recorded simultaneously with charging and discharging of the particles. Structure and dynamics of an anion/MEH-PPV complex, proposed to be responsible for discrete photobleaching in conjugated polymers, have been investigated with this technique. Device physics and kinetics have been elucidated by using the fluorescent conjugated polymer nanoparticles as probes for detecting the presence of hole polarons, and have been related to the electrically induced oxidation and reduction of the anion/MEH-PPV complex.     

Synthesis of hexamethyleneamides of organic acids

Twenty hexamethyleneamides of various organic acids have been synthesized by a direct transamidation reaction. The process consists in the previous mixing of hexamethyleneimine, acetic anhydride, and the corresponding acid, heating the resulting mixture to the boil, and distilling off the acetic acid formed through a fractionating column. The synthesis of amides by this method is characterized by high yields and comparatively short times.