Source Of Organic Acids Research Articles

Short and medium chain organic acids production from hydrolyzed food waste: technical–economic evaluation and insight into the product’s quality

Food waste (FW) was subjected to thermal-alkaline hydrolysis before to be used as source for organic acids (OAs) production under different temperatures and hydraulic regime in long-term acidification process. Mesophilic environment led to the highest acidification yield (0.87 g CODOAs/g VS) with chain-elongation process to caproic acid production (>9.0 g CODcap/L) occurring at lower HRT (2 days). The product’s quality, in terms of OAs production and composition, was evaluated through a multivariate approach, which indicated that the mesophilic condition was also appropriate to steadily maintain the requested product’s features.The specific gas production (SGP) from the solid-rich acidified residue was 0.47 Nm3/kg VS and, in a full-scale scenario of 150,000 kg FW/d, it can be potentially converted into 24.9 MWh/d as electrical energy. Also, according to the acidification performances, an overall OAs production of 7.2 ton/y has been estimated, generating a yearly economic outcome higher than 4,800,000 €.

Nutritional Supplementation of Yogurt with Jerusalem Artichoke Tubers: Organic Acid Profiles and Quality Parameters.

Jerusalem artichoke (Helianthus tuberosus L.), also called wild sunflower, belongs to the Asteraceae family and is cultivated widely across the temperate zone for its nutritious tuber, which is used as a root vegetable. In this study, the Jerusalem artichoke (JA) was used as a supplementary additive for producing a functional yogurt, with enhanced health benefits and improving the microbiological, rheological, and sensorial quality characteristics of the product. The effects of the three different concentrations (1%, 2%, and 3%, w/w) of JA on the physicochemical properties, bacterial counts, sensorial properties, and organic acid profiles of yogurts were determined after 1, 7, 14, and 21 days of storage at ±4 °C. The results obtained revealed that with the addition of different concentrations of JA the overall parameters were statistically significant (p < 0.01 and p < 0.05) except for apparent viscosity, Streptococcus thermophilus, yeast and mold count, pyruvic ratios, and scores of flavor. Similarly, some parameters (fat ratio, yeast and mold count, concentrations of propionic, acetic, pyruvic, orotic, and lactic acids, and scores of appearance, consistency, and odor) changed depending on the storage time, while some did not show any changes regarding storage time. There was a relationship found between the concentration of JA and organic acid ratio (except for pyruvic acid) concentration in the yogurt samples. In conclusion, the research revealed the effect of JA in yogurt production as a thickener, flavor enhancer, prebiotic agent, and source of organic acids and bioactive compounds. The results indicate that JA has a good potential for enhancing the nutritional and physicochemical properties of the studied yogurt.

Ab Initio and RRKM/Master Equation Analysis of the Photolysis and Thermal Unimolecular Decomposition of Bromoacetaldehyde

Bromoacetaldehyde (BrCH2CHO) is a major stable brominated organic intermediate of the bromine-ethylene addition reaction during the arctic bromine explosion events. Similar to acetaldehyde, which has been recently identified as a source of organic acids in the troposphere, it may be subjected to photo-tautomerization initially forming brominated vinyl compounds. In this study, we investigate the unimolecular reactions of BrCH2CHO under both photolytic and thermal conditions using high-level quantum chemical calculations and Rice-Ramsperger-Kassel-Marcus (RRKM)/master equation analysis. The unimolecular decomposition of BrCH2CHO takes place through 14 dissociation and isomerization channels along a potential energy surface involving eight wells. Under the assumption of singlet ground-state potential energy surface-dominated photodynamics, the primary photodissociation yields of BrCH2CHO are investigated under both collision-free and collision energy transfer conditions. At atmospheric pressure and under tropospheric actinic flux conditions at ground level, depending on the assumed collisional energy transfer parameter, 150 cm-1 < ⟨ΔEdown⟩ < 450 cm-1, 78-33% of BrCH2CHO undergoes direct photodissociation instead of collisional deactivation at an excitation wavelength of 320 nm. This is significantly higher than the 14% reported for acetaldehyde, hence indicating a strong effect of bromine substitution on the product photolysis yield that is related to additional favorable Br and HBr forming dissociation channels. In contrast to the overall photodissociation quantum yield, the relative branching fractions of the photodissociation products are less dependent on the collisional energy transfer parameter. For a representative value of ⟨ΔEdown⟩ = 300 cm-1 and an excitation wavelength of 320 nm, with 27% for C-C bond fission, 11% for C-Br bond fission, 7% for HBr elimination, and only below 2% each for a consecutive O-Br fission reaction and the photo-tautomerization channel yielding brominated vinyl alcohol, the photodissociation is markedly different from the acetaldehyde case. Finally, as brominated halogenated compounds are of interest for flame inhibition purposes, thermal multichannel unimolecular rate constants were calculated for temperatures in the range from 500 to 2000 K. At a temperature of 2000 K and ambient pressure, the two main reaction channels are the C-Br and C-C bond fissions, contributing 35 and 43% to the total reaction flux, respectively.

Antioxidant and organic acid evaluation of Geaster saccatum mushroom by chemical and electrochemical assay at carbon nanotube paste electrode

The study was aimed to investigate the antioxidant and organic acid composition of Geaster saccatum mushroom by chemical and electrochemical assay. The antioxidant activity was done by using DPPH and ABTS reagents while the cyclovoltametry (CV) and differential pulse voltamery (DPV) were used to determine its electrochemical behavior at single walled carbon nano tube paste electrode in 0.02 M acetate buffer (pH 5.0), to explore the adsorptive character of its antioxidant compounds at working electrode as a function of pH, scan rate and potential. The organic acid analysis of this mushroom was carried out by High performance liquid chromatography. In DPPH, the scavenging rate was 56.4 ± 0.78%, at 20 µg/ml, reached to 93.4 ± 0.93% at 100 µg/ml, with 61.01 μg/ml as its IC50. Similarly, in ABTS, at same concentrations, scavenging rates were 38.14 ± 0.54% and 95.16 ± 0.43%, with 58.03 μg/ml as its IC50, respectively. HPLC quantified eight organic acids with gallic acid at highest concentration (193.34 mg/kg dry wt) followed by ketoglutaric acid (181.16 mg/kg dry wt.) and oxallic acid (69.54 mg/kg dry wt.). The CV produced a clear irreversible anodic peak at Epa = 0.69 ± 0.01 V, while, ascorbic acid produced a single anodic peak at Epa = 0.29 ± 0.01 V and gallic acid produced two anodic peaks at Epa = 0.41 ± 0.01 V and second at Epa = 0.69 ± 0.01 V. However, only one anodic peak of mushroom was found in DPV at 0.56 ± 0.01 V, which increased proportionally at each increasing concentration of mushroom extract. The results declared this mushroom as one of the best source of organic acids which characterized it as a better antioxidant food as well as medicine.

Analysis and Evaluation of the Characteristic Taste Components in Portobello Mushroom.

The results in this article could provide a theoretical basis for understanding and regulating the characteristic flavor components synthesis process of Portobello mushroom.

Rapid screening and quantification of major organic acids in citrus fruits and their bioactivity studies.

Organic acids (OAs) are small non-volatile molecules with widespread usage in processed foods, feeds and instant beverages. The prime aim of this study was to explore major OAs in local citrus fruits (Citrus limetta, Citrus aurantifolia, Citrus nobilis, Citrus karna, Citrus medica, Citrus ichangensis and Citrus aurantium) and assessment of their bioactivities. A RP-HPLC-DAD method was developed using buffer free solvent system for rapid detection and quantification of major OAs from citrus fruits and derived products. Method validation studies showed good linear calibration curve (0.985-0.998) for all OAs. The values of %RSD ranged between 0.0001-1.129 and 0.142-1.941 for interday and intraday variability respectively. The limit of detection and limit of quantification values for different OAs were ranged between 1.5-12 and 5-40µgmL-1. The juice of above mentioned citrus fruit cultivars were assessed for OAs, total phenolics, free radical scavenging antioxidants and their antimicrobial potential against selected bacterial and fungal strains. The results showed variable contents of phenolics [0.28±0.001-1.17±0.014mg (GAE) mL-1] and antioxidant compounds (1.26±0.009-2.84±0.006mg of trolox equivalents mL-1) in all juice samples besides significant antifungal activity against C. albicans and A. niger strains. However, in case of antibacterial activity, only C. aurantifolia showed inhibitory effects against selected strains. It was found that citrus fruits have immense potential for their utilization as economic source of natural OAs and development of value added products, beverages and bio-preservatives.

The study of biologically active substances of chaenomelesand the products of its processing

The importance of developing food products of improved biological value to ensure the healthy nourishment of the population was analyzed. The prospects of using plant raw materials as a source of biologically active components were shown. The chemical composition of chaenomeles fruit and of the products of its processing was determined. The biological value of the components of the fruit was explored, and it was found that maximum amount of L­ascorbic acid is contained in the pulp of the fruit and that maximum amount of phenolic substances is contained in the peels of the fruit. With the help of chromatographic studies, it was established that the products of chaenomeles processing have significant content of organic acids, among which malic, quinic, citric and succinic acids were identified, malic acid is dominant amomg them. The sugars, found in the fruit of chaenomeles, are represented by fructose, glucose and saccharose, among them fructose and glucose prevail. The raw material contains procyanidins, hydroxycinnamic acids, flavones and flavan­3­ols, among them procyanidin trimmer, chlorogenic acid, rutin and epicatechine dominate, which have high antioxidant properties. In the products of chaenomeles processing, 48 types of aromatic compounds were identified, among which prevail alcohols, acids, ethers and unsaturated carbohydrates that give products of chaenomeles processing unique aroma and predetermine their antibacterial properties. The products of chaenomeles processing (juice, puree) are a valuable source of organic acids; they were used as a natural regulator of acidity and as an antioxidant in manufacturing products from flour yeast dough. Puree fromchaenomeles contains a significant amount of pectic substances and was used in the production of fruit sauces as a structuring agent. An increase in the organoleptic and physical and chemical indicators in fruit sauces and flour products with the use of products of chaenomeles processing was established.

Organic acids in cloud water and rainwater at a mountain site in acid rain areas of South China.

To investigate the chemical characteristics of organic acids and to identify their source, cloud water and rainwater samples were collected at Mount Lu, a mountain site located in the acid rain-affected area of south China, from August to September of 2011 and March to May of 2012. The volume-weighted mean (VWM) concentration of organic acids in cloud water was 38.42μeq/L, ranging from 7.45 to 111.46μeq/L, contributing to 2.50% of acidity. In rainwater samples, organic acid concentrations varied from 12.39 to 68.97μeq/L (VWM of 33.39μeq/L). Organic acids contributed significant acidity to rainwater, with a value of 17.66%. Formic acid, acetic acid, and oxalic acid were the most common organic acids in both cloud water and rainwater. Organic acids had an obviously higher concentration in summer than in spring in cloud water, whereas there was much less discrimination in rainwater between the two seasons. The contribution of organic acids to acidity was lower during summer than during spring in both cloud water (2.20% in summer vs 2.83% in spring) and rainwater (12.24% in summer vs 19.89% in spring). The formic-to-acetic acid ratio (F/A) showed that organic acids were dominated by primary emissions in 71.31% of the cloud water samples and whole rainwater samples. Positive matrix factorization (PMF) analysis determined four factors as the sources of organic acids in cloud water, including biogenic emissions (61.8%), anthropogenic emissions (15.28%), marine emissions (15.07%) and soil emissions (7.85%). The findings from this study imply an indispensable role of organic acids in wet deposition, but organic acids may have a limited capacity to increase ecological risks in local environments.

Compositions and sources of organic acids in fine particles (PM2.5) over the Pearl River Delta region, south China

Organic acids as important constituents of organic aerosols not only influence the aerosols' hygroscopic property, but also enhance the formation of new particles and secondary organic aerosols. This study reported organic acids including C14–C32 fatty acids, C4–C9 dicarboxylic acids and aromatic acids in PM2.5 collected during winter 2009 at six typical urban, suburban and rural sites in the Pearl River Delta region. Averaged concentrations of C14–C32 fatty acids, aromatic acids and C4– C9 dicarboxylic acids were 157, 72.5 and 50.7 ng/m3 respectively. They totally accounted for 1.7% of measured organic carbon. C20–C32 fatty acids mainly deriving from higher plant wax showed the highest concentration at the upwind rural site with more vegetation around, while C14–C18 fatty acids were more abundant at urban and suburban sites, and dicarboxylic acids and aromatic acids except 1,4-phthalic acid peaked at the downwind rural site. Succinic and azelaic acid were the most abundant among C4–C9 dicarboxylic acids, and 1,2-phthalic and 1,4-phthalic acid were dominant aromatic acids. Dicarboxylic acids and aromatic acids exhibited significant mutual correlations except for 1,4-phthalic acid, which was probably primarily emitted from combustion of solid wastes containing polyethylene terephthalate plastics. Spatial patterns and correlations with typical source tracers suggested that C14–C32 fatty acids were mainly primary while dicarboxylic and aromatic acids were largely secondary. Principal component analysis resolved six sources including biomass burning, natural higher plant wax, two mixed anthropogenic and two secondary sources; further multiple linear regression revealed their contributions to individual organic acids. It turned out that more than 70% of C14–C18 fatty acids were attributed to anthropogenic sources, about 50%–85% of the C20–C32 fatty acids were attributed to natural sources, 80%–95% of dicarboxylic acids and 1,2-phthalic acid were secondary in contrast with that 81% of 1,4-phthalic acid was primary.

Chemical characteristics and sources of organic acids in precipitation at a semi-urban site in Southwest China

In order to investigate the chemical characteristics and sources of organic acids in precipitation in Southwest China, 105 rainwater samples were collected at a semi-urban site in Anshun from June 2007 to June 2008. Organic acids and major anions were analyzed along with pH and electrical conductivity. The pH values varied from 3.57 to 7.09 for all the rainfall events sampled, with an average of 4.67 which was typical acidic value. Formic, acetic and oxalic acids were found to be the predominant carboxylic acids and their volume weighted average (VWA) concentrations were 8.77, 6.93 and 2.84 μmol l−1, respectively. These organic acids were estimated to account for 8.1% to the total free acidity (TFA) in precipitation. The concentrations of the majority organic acids at studied site had a clear seasonal pattern, reaching higher levels during the non-growing season than those in growing season, which was attributed to dilution effect of heavy rainfall during the growing season. The seasonal variation of wet deposition flux of these organic acids confirmed higher source strength of biogenic emissions from vegetation during the growing season. Formic-to-acetic acids ratio (F/A), an indicator of primary versus secondary sources of these organic acids, suggested that primary sources from vehicular emission, biomass burning, soil and vegetation emissions were dominant sources. In addition, the lowest concentrations of organic acids were found under type S, when air masses originated from the marine (South China Sea) during Southern Asian Monsoon period. And the highest concentrations were observed in precipitation events from Northeast China (type NE), prevailing mostly during winter with the lowest rainfall.

The role of organic acid exudates in liberating phosphorus from seagrass‐vegetated carbonate sediments

Sediment‐bound phosphorus (P) is a potential nutrient source for P‐limited seagrasses inhabiting carbonate sediments. We explored the role of organic acid (OA) exudation by seagrasses in liberating mineral P from carbonate sediments. Organic acids can act to increase available P by dissolving carbonate sediment, competing with P for binding sites and complexing dissolution end products, and also by fueling microbial processes that change pore‐water pH. We used dialysis tubing placed around individual roots in situ to quantify dissolved species immediately adjacent to roots (root zone) and compared these to bulk pore‐water concentrations in vegetated and nonvegetated sediments. Total OA concentrations were highest in the root zone (29.8 ± 1.8 [mol L−1) compared to bulk measures of 15.5 ± 1.9 and 7.5 ± 0.6 [mol L−1 in vegetated and nonvegetated sediments, respectively. Phosphate concentrations were also highest in the root zone and were linearly related to OA concentrations (R2 = 0.63). Organic acid concentrations increased along a seagrass productivity gradient, and ratios of OA concentrations to productivity showed a significant response to a gradient in P‐limitation of seagrasses. Organic acid concentrations found in and around roots, compared to those found in bulk sediment measures, indicate that seagrasses are a significant source of OA. Sampling at small spatial scales (mm) immediately adjacent to the roots is critical, because bulk sediment pore‐water measures did not capture the observed fluctuations caused by the rapid reaction and consumption of OA in the sediment. Root‐zone processes can liberate considerable quantities of P, and OA exudates likely contribute significantly to the success of T. testudinum in P‐limited environments.

On the Source of Organic Acid Aerosol Layers above Clouds

During the July 2005 Marine Stratus/Stratocumulus Experiment (MASE) and the August-September 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS), the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter probed aerosols and cumulus clouds in the eastern Pacific Ocean off the coast of northern California and in southeastern Texas, respectively. An on-board particle-into-liquid sampler (PILS) quantified inorganic and organic acid species with < or = 5-min time resolution. Ubiquitous organic aerosol layers above cloud with enhanced organic acid levels were observed in both locations. The data suggest that aqueous-phase reactions to produce organic acids, mainly oxalic acid, followed by droplet evaporation is a source of elevated organic acid aerosol levels above cloud. Oxalic acid is observed to be produced more efficiently relative to sulfate as the cloud liquid water content increases, corresponding to larger and less acidic droplets. As derived from large eddy simulations of stratocumulus underthe conditions of MASE, both Lagrangian trajectory analysis and diurnal cloudtop evolution provide evidence that a significant fraction of the aerosol mass concentration above cloud can be accounted for by evaporated droplet residual particles. Methanesulfonate data suggest that entrainment of free tropospheric aerosol can also be a source of organic acids above boundary layer clouds.

Exchange of short‐chain monocarboxylic acids by vegetation at a remote tropical forest site in Amazonia

As part of the project LBA‐EUSTACH (European Studies on Trace gases and Atmospheric Chemistry as a contribution to the Large‐Scale Biosphere‐Atmosphere experiment in Amazonia), the exchange of formic acid and acetic acid between vegetation and the atmosphere was investigated in the wet‐to‐dry season transition and the dry‐to‐wet season transition periods in 1999 in Rondônia, Brazil. Direct exchange measurements on the branch level mainly exhibited uptake of formic acid and acetic acid for all plant species in both seasons, although diel, seasonal, and interspecies variations were observed. Even though other physiological and physico‐chemical parameters may have contributed, the uptake of organic acids was found to be primarily a function of the ambient atmospheric mixing ratios. The linear dependence suggests a bidirectional exchange behavior of the plants and calculated deposition velocities (0.17–0.23 cm s−1), compensation point mixing ratios (0.16–0.30 ppb), and potential emission rates under purified air conditions (0.013–0.031 nmol m−2 s−1) are discussed. Vertical profile measurements in and above the primary forest canopy further strengthened the assumption that the forest is rather a sink than a source for organic acids. The generally lower mixing ratios observed within the canopy were indicative of an uptake by vegetation and/or the soil surface. Continuous measurements of the ambient atmospheric mixing ratios at the canopy top revealed strong diel variations in both seasons and a marked seasonality with higher mixing ratios during the dry season, both being mirrored in the variation of observed uptake rates of the plants. High atmospheric concentrations during the dry season were attributed to biomass burning. During the wet season, when biomass burning activity was low, indirect emission by the vegetation, i.e., photochemical oxidation of primarily emitted biogenic reactive hydrocarbons, was assumed to dominantly contribute to the atmospheric burden of the organic acids. The high degree of correlation between atmospheric formic acid and acetic acid indicated that similar atmospheric processes were affecting their mixing ratios.

Organic geochemical studies of soils from the Rothamsted classical experiments — VI. The occurrence and source of organic acids in an experimental grassland soil

Total lipid extracts (TLEs) of grass (aerial and sub-aerial, Holcus lanatus) from a plot on a long-term grassland experiment, and associated soil, along with the organic fraction of the TLE hydrolysates and the hydrolysates of the solvent extracted vegetation have been separated into fractions containing specific compound classes and analysed using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The distributions of n-alkylcarboxylic acids, ω-hydroxycarboxylic acids and dicarboxylic acids in the grass and the underlying soil have been determined. Short-chain (<C 20) n-alkylcarboxylic acids were designated as having derived from both aerial and sub-aerial vegetation. However, longer-chain n-alkylcarboxylic acids were ascribed to suberin as a predominant source. Moreover, ω-hydroxycarboxylic acids and dicarboxylic acids observed in the soil were designated as having predominantly derived from inputs of free, extractable polyesters and suberin intimately associated with plant roots. This study indicates the importance of root material as a predominant source of aliphatic, organic acids in the soil of temperate grassland biomes.

Aqueous-phase photolysis of biacetyl (An α-dicarbonyl compound): A sink for biacetyl, and a source of acetic acid, peroxyacetic acid, hydrogen peroxide, and the highly oxidizing acetylperoxyl radical in aqueous aerosols, fogs, and clouds

Aqueous-phase photolysis of biacetyl represents a heretofore uncharacterized sink for biacetyl and source of organic acids and peroxides to aqueous aerosols, and fog and cloud drops. The photolysis half-life of aqueous-phase biacetyl is approximately 1.0–1.6 h for a solar zenith angle of 36° (midday equinox sunlight in Durham, NC). Major products of aqueous biacetyl photolysis are acetic acid, peroxyacetic acid, and hydrogen peroxide. Pyruvic acid and methylhydroperoxide are minor photoproducts. Common atmospheric reductants (H-atom donors), such as formate, formaldehyde, glyoxal, phenol (as a model for phenolic compounds) and α- d-glucose (as a model for carbohydrates), substantially increase the quantum yields of peroxyacetic acid Formate also significantly increases the quantum yields of hydrogen peroxide. The highly oxidizing acetylperoxyl radical is proposed as a key intermediate in the photolysis of aqueous biacetyl. The sources and reactions of acetylperoxyl radicals in aqueous aerosols, fogs, and clouds should be investigated in future studies of atmospheric water-drop chemistry.

Microbial acetogenesis as a source of organic acids in ancient Atlantic Coastal Plain sediments

Research Article| October 01, 1996 Microbial acetogenesis as a source of organic acids in ancient Atlantic Coastal Plain sediments Francis H. Chapelle; Francis H. Chapelle 1U.S. Geological Survey, 720 Gracern Road, Suite 129, Columbia, South Carolina 29210 Search for other works by this author on: GSW Google Scholar Paul M. Bradley Paul M. Bradley 1U.S. Geological Survey, 720 Gracern Road, Suite 129, Columbia, South Carolina 29210 Search for other works by this author on: GSW Google Scholar Author and Article Information Francis H. Chapelle 1U.S. Geological Survey, 720 Gracern Road, Suite 129, Columbia, South Carolina 29210 Paul M. Bradley 1U.S. Geological Survey, 720 Gracern Road, Suite 129, Columbia, South Carolina 29210 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1996) 24 (10): 925–928. https://doi.org/10.1130/0091-7613(1996)024<0925:MAAASO>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Francis H. Chapelle, Paul M. Bradley; Microbial acetogenesis as a source of organic acids in ancient Atlantic Coastal Plain sediments. Geology 1996;; 24 (10): 925–928. doi: https://doi.org/10.1130/0091-7613(1996)024<0925:MAAASO>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Field and laboratory evidence shows that deeply buried (90–888 m) fine-grained sediments of the Atlantic Coastal Plain contain viable acetogenic microorganisms, and that these microorganisms actively produce organic acids. Concentrations of formate, acetate, and propionate in pore waters extracted from fine-grained sediments ranged from 50 μM to 5 mM and were much higher than in adjacent pore waters associated with sandy sediments (<2 μM). Laboratory studies showed that asceptically cored fine-grained sediments incubated under a H2 atmosphere produced formate and acetate, and that H14CO3− was converted to 14C-acetate and 14C-formate over time. An enrichment culture of these acetogenic microorganisms was recovered from one long-term incubation that showed the presence of several morphologically distinct gram-positive, rod-shaped bacteria. These microorganisms were capable of growth under autotrophic (H2 + CO2), heterotrophic (syringate), and mixotrophic (H2 + CO2 + syringate) conditions. These results suggest that microbial acetogenesis, rather than abiotic processes, is the most important organic acid-producing mechanism during low-temperature (∼ 30 °C) diagenesis of Atlantic Coastal Plain sediments. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Evaluation of proposed precipitation mechanisms for Mississippi Valley-type deposits

The mechanism of precipitation is an important aspect of any genetic model for Mississippi Valley-type deposits. Yet most of the precipitation mechanisms for minerals in the Mississippi Valley-type association have serious flaws. Solution mixing would require an unlikely series of solutions to account for the various minerals in the ores, and it does not account for the universal occurrence of organic matter in the ores nor for the oxidation state of sulfur in pyrite in the ores. Sulfate reduction addresses some of these problems, but is inconsistent with kinetic data and could not be reversed to account for the oscillations between precipitation and dissolution of sulfide minerals in the ores. Carbon dioxide effervescence does not address the precipitation of most minerals in the ores, and all of the evidence for effervescence may be explained in other ways. Cooling of the mineralizing solution could precipitate many minerals, but fluid inclusion data suggest that, in many deposits, the solution did not cool significantly as any particular stage formed. A credible genetic model also must explain why all of the minerals precipitated at the same sites; any combination of the above mechanisms which suggests that unrelated mechanisms occurred at the same sites by coincidence is unlikely. The most reasonable scenario is that a hot, thiosulfate-bearing mineralizing solution reacted in various ways with organic matter at the sites of mineralization to precipitate the ore minerals. The organic matter acted as a reductant, source of carbon dioxide, source of organic acids, and a substrate for bacterial metabolism of thiosulfate in various stages of mineralization. Thus organic matter links all stages of the mineralization to the same sites.

Behavior of atmospheric formic and acetic acid in the presence of hydrometeors

The partitioning of formic and acetic acid between the atmospheric liquid and gaseous phase is modelled for a range of liquid water contents. At low liquid water content, formic acid is dissolved preferentially over acetic acid. Applying these results to the analysis of processes taking place in clouds, one can explain the frequently found enrichment of formic over acetic acid in rainwater, which results from selective transport by washout. We assess the ability of dew to act as a temporary sink and source for organic acids, and propose that the diel variation of mixing ratios often found during surface measurements, may in part be due to the dissolution in dew and subsequent evaporation on the following day.

Isotachophoresis of organic acids after oxidation of hydrolytic products of some monosaccharides

One of the basic components of cultivation media for microorganisms at biotechnological processes are organic compounds as the source of organic acids. Optimal conditions were found for separation of organic acids by isotachophoresis. The products of the alkaline degradation of glucose and their oxidation products after successive glucose oxidation were tested.

An hypothesis of function for the avian glycogen body: A novel role for glycogen in the central nervous system

Our own and other recent data have led us to hypothesize that the glycogen body, heretofore generally considered to be metabolically inert, may be functionally geared to support the process of myelin formation in the avian central nervous system (CNS). We envision that the abundant glycogen stores in this tissue, unlike those in the liver or in skeletal muscle, can serve as a recyclable substrate for the ultimate production of reducing equivalents that would be available for the synthesis of myelin lipid cholesterol. In addition, it is suggested that such glycogen also may serve as a source of organic acids which might provide alternate substrates to the CNS under conditions of metabolic stress.