Site-specific (13) С/(12) С isotope abundance ratios in dicarboxylic oxyacids as characteristics of their origin

RATIONALE

Recommendations of relevant international organizations controlling the quality of grape wines and beverages specify that only tartaric acids of grape origin can be introduced to achieve the required parameters. The development of methods for determining the origin of tartaric acid in grape wine is of great technological significance.

METHODS

Organic dicarboxylic oxyacids were extracted from wines as barium salts. Carbon dioxide, which included all the carbon atoms of the acids, was used to determine the carbon isotope ratios by Isotope Ratio Mass Spectrometry. The alkyl part of the oxyacids was burned at 560°C in the presence of air; BaCO3 containing the carboxyl carbon was left. This carbonate was used to measure the carbon isotope ratios in the carboxyl part of the acid. The carbon isotope ratios of the alkyl part of tartaric acid were found by isotope mass balance.

RESULTS

The carbon isotope composition of carboxyl groups (δ(13) С values) in tartaric acid of grape (biogenic origin) had a higher (13) С content than the carbon in the alkyl part of the molecule. Tartaric acid produced by chemical synthesis (abiogenic origin) was noted to have a different (13) С/(12) С distribution: the carboxyl group of tartaric acid produced by chemical synthesis contained a smaller than or equal amount of (13) С to the alkyl part.

CONCLUSIONS

This is the first determination of the site-specific distribution of the (13) С/(12) С isotopes in tartaric acids as evidence of their biogenic and abiogenic origins. The presented method for determining the origin of tartaric acid can be used for efficient control of the quality of grape wines and beverages.

[Bioremediation of oil-polluted soils: using the [13C]/[12C] ratio to characterize microbial products of oil hydrocarbon biodegradation]

We compared data on the extent of bioremediation in soils polluted with oil. The data were obtained using conventional methods of hydrocarbon determination: extraction gas chromatography-mass spectrometry, extraction IR spectroscopy, and extraction gravimetry. Due to differences in the relative abundances of the stable carbon isotopes (13C/12C) in oil and in soil organic matter, these ratios could be used as natural isotopic labels of either substance. Extraction gravimetry in combination with characteristics of the carbon isotope composition of organic products in the soil before and after bioremediation was shown to be the most informative approach to an evaluation of soil bioremediation. At present, it is the only method enabling quantification of the total petroleum hydrocarbons in oil-polluted soil, as well as of the amounts of hydrocarbons remaining after bioremediation and those microbially transformed into organic products and biomass.

[Ratio [13C]/[12C] as an index for express estimation of hydrocarbon-oxidizing potential of microbiota in soil polluted with crude oil]

The hydrocarbon-oxidizing potential of soil microbiota and hydrocarbon-oxidizing microorganisms introduced into soil was studied based on the quantitative and isotopic characteristics of carbon in products formed in microbial degradation of oil hydrocarbons. Comparison of CO2 production rates in native soil and that polluted with crude oil showed the intensity of microbial mineralization of soil organic matter (SOM) in the presence of oil hydrocarbons to be higher as compared with non-polluted soil, that is, revealed a priming effect ofoil. The amount of carbon of newly synthesized organic products (cell biomass and exometabolites) due to consumed petroleum was shown to significantly exceed that of SOM consumed for production of CO2. The result of microbial processes in oil-polluted soil was found to be a potent release of carbon dioxide to the atmosphere.

Estimation of microbial methane generation and oxidation rates in the municipal solid waste landfill of Kaluga city, Russia

Using a theoretical model and mass isotopic balance, biogas (methane and CO(2)) released from buried products at their microbial degradation was analysed in the landfill of municipal and non-toxic industrial solid organic waste near Kaluga city, Russia. The landfill contains about 1.34 x 10(6) tons of waste buried using a 'sandwich technique' (successive application of sand-clay and waste layers). The delta(13)C values of biogenic methane with respect to CO(2) were-56.8 (+/-2.5) per thousand, whereas the delta(13)C of CO(2) peaked at+9.12 per thousand (+1.4+/-2.3 per thousand on average), reflecting a virtual fractionation of carbon isotopes in the course of bacterial CO(2) reduction at the landfill body. After passing through the aerated soil layers, methane was partially oxidised and characterised by delta(13)C in the range of-50.6 to-38.2 per thousand, evidencing enrichment in (13)C, while the released carbon dioxide had delta(13)C of-23.3 to-4.04 per thousand, respectively. On the mass isotopic balance for the delta(13)C values, the methane production in the landfill anaerobic zone and the methane emitted through the aerated landfill surface to the atmosphere, the portion of methane oxidised by methanotrophic bacteria was calculated to be from 10 to 40% (averaged about 25%). According to the theoretical estimation and field measurements, the annual rate of methane production in the landfill reached about 2.9(+/-1.4)x10(9) g C CH(4) yr(-1) or 5.3(+/-2.6)x10(6) m(3) CH(4) yr(-1). The average rates of methane production in the landfill and methane emission from landfill to the atmosphere are estimated as about 53 (+/-26) g C CH(4) m(-2) d(-1) (or 4 (+/-2) mol CH(4) m(-2) d(-1)) and 33 (+/-12) g C CH(4) m(-2) d(-1) (or 2.7 (+/-1) mol CH(4) m(-2) d(-1)), respectively. The calculated part of methane consumed by methanotrophic bacteria in the aerated part of the landfill was 13(+/-7) g C CH(4) m(-2) d(-1) (or 1.1(+/-0.6) mol CH(4) m(-2) d(-1)) on average.

[Evaluation of glucose utilization in patients with insulin-independent diabetes mellitus by using breathing test]

Commonly used clinical and biochemical parameters, such as the content of glucose, insulin, somatotropic hormone, triglycerides, lactate, pyruvate, and free fatty acids (FFA) in blood of practically healthy subjects and in patients with insulin-independent diabetes mellitus (IIDM), were compared with the parameters obtained by mass-spectrometric analysis of 13CO2 in expired air after 13C-glucose loading. It was shown that, as opposed to healthy subjects, the content of blood glucose and free fatty acids in patients with IIDM increased, the level of glucose dropped in progression upon short-term fasting, and the concentration of lactate changed both upon fasting and after the administration of small test doses of glucose. The use of the 13C-glucose breathing test (13C-GBT), which presupposes the loading of safe small doses of glucose enriched in 13C-isotope permitted one to reveal a number of novel quantitative diagnostic criteria for the evaluation of glucose metabolism in patients with IIDM: a decrease in the rate of 13C withdrawal as a constituent of expired carbon dioxide after the administration of 13C-glucose; a reduction in the amount of exogenous glucose metabolized to carbon dioxide; and increased oxidation of endogenous substrates participating in carbon dioxide formation. Small glucose loads proposed by the authors in 13C-GBT are safe for patients with diabetes mellitus and have no effect on the level of blood glucose in healthy persons. The parameters determined by noninvasive 13C-GBT are more sensitive for diagnosis than commonly used biochemical characteristics of blood in patients with IIDM. The diagnostic criteria obtained allow the prediction of the maximum prohibited glucose loading for every patient.

[The Use of the abundance ratio of 13C and 12C isotopes for characteristic of the origin of ethyl alcohol]

During alcohol fermentation, the carbon isotope composition of ethyl alcohol produced depended on the substrate used and was characterized by the value of delta 13C equal to -24.7 +/- 0.8/1000 (wheat grain), -22 +/- 0.1/1000 (rye grain), -22 +/- 0.5/1000 (products of wood hydrolysis), -15.3 +/- 0.3/1000 (maize grain) and -10 +/- 0.1/1000 (sugar cane). The isotope composition of carbon of ethyl alcohol obtained during catalytic hydroxylation of ethylene has a delta 13C of -30.6 +/- 0.3/1000. The possibility of quantitative determination of specific components in mixtures of ethanol samples with various isotope compositions (chemical synthesis and alcohol fermentation of raw material from C3- or C4-plants) was shown.