Browsing by Subject "Kohlendioxid"

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    Einfluss von erhöhtem atmosphärischen CO2 auf die N2-fixierende Symbiose von Trifolium repens L. und Rhizobium leguminosarum biovar trifolii
    (2007) Stöber, Sara; von Wirén, Nicolaus
    CO2 is one of the main greenhouse gases strongly influencing the climate and the terrestrial ecosystem. Up to know little is known about the impact of elevated atmospheric CO2 on symbiotic interactions in the rhizosphere, especially on the N2-fixing symbiosis between Trifolium repens and Rhizobium leguminosarum biovar trifolii. First results of a ten-year Free-Air CO2 enrichment experiment (Swiss FACE) showed that after three years of CO2 fumigation the genetic composition of the Rhizobium population in the root nodules of T. repens had changed. The first part of this thesis set out to clarify the question whether a genetic difference in the Rhizobium population of root nodules of white clover could still be detected after ten years of CO2 fumigation or if an adaptation of the nodule bacteria to elevated CO2 concentrations had occurred. Furthermore the thesis addressed the question whether elevated atmospheric CO2 leads to quantitative and qualitative changes in the root exudation of T. repens particularly with regard to exudation of signal substances during the nodulation process. In summer 2002 white clover plants were collected from plots fumigated with CO2 and control plots of the Swiss FACE. Rhizobium strains were isolated from the clover root nodules and used for rep-PCR DNA fingerprinting. Results clearly showed that after ten years of CO2 enrichment changes in the genetic composition of the R. l. bv. trifolii could no longer be observed. Thus, CO2-induced changes in the population structure of rhizobia seemed to be transient. This can be traced back to the possibility that over the experimental period a new C/N equilibrium in the grassland ecosystem has been established. At the beginning of the FACE experiment an increase in the C/N ratio of the soil was detected, which could be balanced in the course of time through enhanced symbiotic N2 fixation and consequently a higher N input into the ecosystem. The observed stabilisation of the grassland ecosystem most likely caused a reduction of the indirect CO2 impact on the microorganisms. This might explain why a change in the genetic composition of Rhizobium strains was not longer detected after ten years in the Swiss FACE. To investigate an influence of elevated atmospheric CO2 concentration on the release of signalling compounds clover plants were cultivated hydroponically in two independent climate chamber trials under axenic and non-axenic conditions at ambient and elevated CO2 concentrations (400 and 800 ppm) and different levels of N supply. Root exudates were collected over a period of seven hours and at three and four different plant ages, respectively. Phenolic compounds were extracted by solid-phase extraction and afterwards analysed with HPLC and LC-MS. Additionally, the isolated fractions were tested for their ability to induce the nodulation genes of R. l. bv. trifolii using a nod-gene induction test. The CO2 enrichment caused an increase in shoot and root growth in both experimental setups, but did not provoke a change in the C/N ratio of the roots. Besides the known signal compound 7,4?-dihydroxyflavone new phenolic substances could be detected, which have not yet been described in literature. The fractions were identified by their polarity, light absorption and molecular weight as aglyca and flavones. All of these had the ability for nod-gene induction except one fraction (fraction 2). CO2 influenced the exudation of signalling compounds quantitatively but not qualitatively. The enhanced exudation, especially of 7,4?-dihydroxyflavone, could be attributed to the higher root mass under elevated CO2 but also to a higher release rate on a root fresh weight basis. The CO2 reaction of the clover plants, for the biomass production as well as for the root exudation, was clearly dependent on the N supply and only significant under axenic conditions. In individual cases the N impact was more pronounced than the CO2 effect: with increasing N demand axenic clover plants enhanced the exudation of the nod-gene inducing fraction C. It is concluded that this fraction, identified as a hydroxyflavone, has therefore an important signal function under N limitation. Besides the CO2 concentration and N supply, root exudation by T. repens was considerably influenced by the plant age, which caused a reduction of the signal exudation in older plants and qualitative changes of the released phenols, especially under non-axenic conditions. The present study suggests that the genetic shift of R. l. bv. trifolii detected at the beginning of the Swiss FACE experiment was most likely a consequence of the enhanced exudation of phenolic signal compounds of T. repens under elevated atmospheric CO2 concentrations.
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    Production of CO₂ gas hydrates with its application in wheat bread making process
    (2023) Srivastava, Shubhangi; Hitzmann, Bernd
    The basic requirements necessary for gas hydrate (GH) formation are low temperature, high pressure, the presence of guest molecules, and the desired amounts of water molecules. The most common guest molecules used for the GH are ethane, methane, butane, propane, nitrogen, and carbon dioxide. Hydrate based technological applications almost always require rapid hydrate formation along with high gas uptake to be economically viable. One possible approach to achieving the same is the introduction of particular additives into the system. These additives are known as hydrate promoters. In recent times, amino acids have emerged as a highly effective class of promoters, and unlike surfactants, they promise a clean mode of kinetic action, i.e., no foam formation. Hence, the first part of the thesis dealt with the optimisation of GH formation with the application of amino acid promoters. The optimisation of the GH production was performed with different combinations of promoter ingredients namely cysteine, valine, leucine, and methionine. The amino acids leucine and methionine gave some positive results with the application of promoters for the production of GH therefore, these two amino acids were carried further for the experimentation purpose in the production of GH. Also, a combinational use of these amino acids (leucine and methionine) was studied to investigate the effect on percentage CO₂ retention in comparison to the normal water GH. The conventional baker’s yeast, Saccharomyces cerevisiae, remains the popular leavening agent in the bread baking industry. Carbon dioxide required for the rising of dough is produced by the metabolism of yeast with the consumption of sugars in the dough, which is a time and energy-consuming process. This research attempts to utilize carbon dioxide gas hydrate as a leavening agent in bread. Despite plentiful experiments on CO₂ gas hydrates in other fields, there is still an urge to carry out more analysis to elucidate various applications of GH in baking and positively validate its sustainability. The temperature stability of GH is important while baking due to the exposure to high temperatures during the various steps involved. In order to effectively use CO₂ GH as a leavening agent in the baking industry, a concise evaluation of the formation of CO₂ GH and its gas containment capacity should be adequately analysed and documented. Also, the effect of CO₂ GH properties by the addition of promoters should be taken into consideration as baking involves higher temperatures, and stabilising the GH at higher temperatures is an important criterion in the context of baking different products. Hence, the effect of a higher temperature of 90 ℃; on the CO₂ gas entrapment of the produced GH with promoters was studied. It was observed that the stability of GH decreases with an increase in temperature, but the addition of promoters, especially leucine + methionine + lecithin increased the CO₂ uptake during GH formation. Another part of the thesis was the application of GH in the baking bread with/without promoters and the study of physio chemical properties of bread. By varying the percentage of gas hydrates from 10-60 %, analysis of the performance of CO₂ GH as a leavening agent during baking was done. The effectiveness of GH bread was evaluated by comparing its characteristics to those of standard bread made with yeast. Also, a comparative evaluation was made for bread with and without promoters GH as leavening agents in terms of different physio chemical characteristics of the bread, such as moisture analysis, volume analysis, pore analysis, texture profile analysis, and baking loss. The results show that the bread with 20 % and 40 % GH obtained the best results in terms of volume and pore size. The next part of the thesis dealt with a comparative analysis of the partial replacement of yeast with CO₂ GH as leavening agents in bread baking. By partially eliminating the yeast, variations of bread dough were produced by the addition of GH in different percentages (20-70 %). The effectiveness of GH on bread manufacture was evaluated by comparing its characteristics to that of standard bread made with yeast. Once the bread was baked, the texture profile, volume, moisture content, and pore size were recorded to compare the leavening effect of GH with the standard recipe when partial addition of yeast was done. The best results combinations with respect to specific volume, pore analysis and hardness were obtained with 70 % GH + 50 % yeast and 70 % GH + 75 % yeast, respectively. As the final part of the thesis, the influence of additives on wheat bread baked with promoter induced CO₂ GH as leavening agents was studied. The additives used for the study were ascorbic acid (AC), egg white (EW), and rice flour (RF). These additives were added to the GH bread containing different amounts of GH (40, 60, and 70 % GH). Also, a combination of these additives in a wheat GH bread recipe was studied for each respective percentage of GH. Based on the results of the study, it was found that 70 % GH+ AC+EW+RF wheat bread was found to be the best in terms of textural analysis, pore size analysis, and other physiochemical parameters. Therefore, this research study will help us in understanding the application of GH in the bread baking process with replacement of conventional baking agents such as yeast.
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    Reaktionen einer Weizen-Wildkraut Gemeinschaft auf erhöhtes CO2 im FACE Experiment: Proteomik, Physiologie und Bestandesentwicklung
    (2006) Weber, Simone; Fangmeier, Andreas
    The enhancement of the atmospheric carbon dioxide concentration in the last 150 years due to human activities is one of the main components of global change. For the future, different scenarios predict a steadily increase of carbon dioxide in our atmosphere. As carbon dioxide is the most important carbon source for plants, higher CO2 concentrations have the potential to cause direct effects on plant metabolism and vegetation development. Until now almost all of the studies concerning the effects of elevated CO2 on plants were carried out under controlled conditions, whereas the effects under natural conditions are in-vestigated at only 33 sites worldwide. The aims of this study were to investigate the effects of elevated carbon dioxide on a plant community under natural conditions with regard of (i) the plant proteome, (ii) the plant physiology, (iii) the vegetation development and (iv) the potential interactions between these criteria. Therefore a Mini-FACE system was used to expose a plant community composed of wheat and weeds to two different treatments: (a) Ambient (ambient CO2 concentration, circa 380 ppm) and (b) FACE (Ambient + 150 ppm CO2). The study mainly focussed on the bio-chemical and physiological reactions of spring wheat (Triticum aestivum cv. Triso) as a crop species and wild mustard (Sinapis arvensis L.) as a weed species on carbon dioxide enrich-ment. The SELDI-TOF-MS technology was applied for the first time in the topic of carbon dioxide impacts on plants. The technology provides the opportunity to quantitatively and qualitatively investigate low molecular weight proteins with low abundances, which has been difficult to realise with the standardized methodology in proteomics until now. In addition to the biochemical and physiological analysis, the vegetation development was investigated continuously during the vegetation period using non-destructive methods. This included the assessment of species phenology and species dominance. The results of the performed study show that the carbon dioxide enrichment affects the protein profiles of both species wheat and wild mustard. Interestingly, many alterations in the protein concentrations were found, but no protein could be detected to be exclusively ex-pressed under CO2 treatment. The degree of modification in both species was influenced by their developmental stage. Particularly the protein profile of wheat leaves was strongly in-fluenced during generative plant development, therefore the plants seems to be highly sensitive to environmental changes during this developmental stage. Altogether three proteins were identified which were affected by CO2 treatment. The first protein, the saccharose-H+-symporter protein, was detected in the grain of spring wheat and is associated with the plant?s primary metabolism. This protein plays an important role in controlling the import of saccharose in developing grain. Consequently, elevated CO2 seems to regulate the allocation of assimilates in an active way by influencing the saccharose-H+-symporter concentration in the grain of spring wheat. Furthermore, the remaining two proteins, the PR4 protein localized in the grains and the LRR-kinase protein accumulated in the leaves of spring wheat, are associated with the secondary plant metabolism and they also responded to the elevated CO2 concentrations. These proteins are linked with defense reactions of the plants against patho-gens. The elevated CO2 concentrations caused a decrease in defense recognition in the vege-tative tissue. If the plant is infected by pathogens this down-regulation could result in a ne-gative impact. The concentration of soluble proteins and of total nitrogen decreased in the leaves of spring wheat whereas the C/N ratio increased. Despite this the relative concentration of Chlorophyll a was not affected and therefore an accelerated growth of the plants due to the carbon dioxide enrichment can be excluded. Thus the detected pattern of responses suggests an enhanced nitrogen use efficiency under increased CO2 concentrations. The biomass of single spring wheat plants was unaltered during the vegetation period whereas other investi-gations in parallel showed an enhanced growth and a greater yield of spring wheat at the end of the vegetation period. Species dominance of wheat and weeds was neither influenced in the first nor the second year of investigation with regard to CO2 enrichment. The results indicate that annual crop systems under natural conditions indeed exhibit strong reactions concerning proteomics and physiology, but not concerning the plant development probably due to a relative short time of exposition. Based on long term considerations the detected reactions of the plant proteome may play an important role in the breeding of optimal adapted plants.
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    Ultraschallbasierte simultane Konzentrationsbestimmung der Komponenten Zucker und Ethanol in wässrigen Fermentationsfluiden
    (2014) Schöck, Thomas; Hitzmann, Bernd
    At alcoholic fermentation processes in aqueous solutions there are converted various sugars (mono-, di- and polysaccharides) into ethanol and carbon dioxide by diverse intermediate steps. In the industrial production, ultrasound based methods for the analysis of the composition of the fermentation fluid are advantageous due to their robustness, price cheapness and the possibility for the accomplishment of on line measurements. Within the scope of the present work there are presented several methods for the simultaneous determination of the sugar and ethanol content in the fermentation fluid based on the analysis of ultrasound parameters, also at the presence of dissolved carbon dioxide gas, and compared with respect to the accuracy of their predictive values. Initially there is investigated the behavior of the parameters sound velocity and adiabatic compressibility in standardized aqueous fluids in dependency of the concentration of the components sugar (2 -16 mass percent) and ethanol (1- 6 mass percent), the CO2 partial pressure (0 – 3,013E+05 Pa) and the temperature (2 – 30° C). Thereby the disaccharide saccharose acts as a model substance for the sugar fraction. From the data field of the sound velocity two polynomial calibration models for the sugar / ethanol concentration are extracted with the methods of the multiple linear regression (MLR) and the partial least squares (PLS-) analysis. The minimal accessible standard deviation of the concentration values determined by the particular model from the reference values lies for the MLR method at 0,6 mass percent for the sugar and 0,2 mass percent for the ethanol fraction. The PLS-analysis yields a standard deviation for the sugar and ethanol values of 0,36 and 0,13 mass percent respectively (fluids without a CO2 fraction), as well as 0,5 / 0,17 mass percent (fluids including a CO2 fraction). A further analytic method uses a linearized model of the adiabatic compressibility and the density for the sugar / ethanol determination. The analysis of two physical parameters at this method yields a significant increase of the model quality. For fluids without a CO2 fraction there is reached a minimal standard deviation of 0,06 mass percent for the sugar and 0,07 mass percent for the ethanol concentration. For CO2 containing fluids the corresponding values results to 0,06 / 0,13 mass percent.