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Study of the Selected Types of Sulphur Compounds in Beer and Brewing Materials
Mikulíková, Renata ; Ventura, Karel (referee) ; Ventura, Karel (referee) ; Čáslavský, Josef (referee) ; Márová, Ivana (advisor)
Much attention has been recently devoted to sensorially active substances affecting beer quality in the Czech Republic and worldwide. Among them, the heterocyclic and sulphur containing compounds play an important role, some of them with high sensorial activity even in extremely low concentrations. Trace amounts of these compounds, which can be frequently found in foods, participate in formation of their aroma and this effect can be generally evaluated as favorable However, in malt or beer it is true only to a limited extent and the presence of heterocyclic and sulphur containing compounds are in this respect assessed rather unfavorably. The aim of the present study was to provide a survey about of problems in the field of sulphur containing compounds in barley, malt and beer, to describe metabolic paths leading to their formation and to verify experimentally possibilities of their determination using modern analytical methods. Sulphur-containing amino acids are a natural part of barley, malt and beer and are precursors of the origin of volatile sulphur substances. The most frequently occurring sulphur amino acids, metionine, cysteine and homocysteine, were selected for analytical monitoring. The method of gas chromatography was used to determine sulphur-containing amino acids in barley, malt and beer. Prior to the analysis, sulphur-containing amino acids were derived and volatile N(O,S)-ethoxycarbonyl propyl esters were formed; they were subsequently analyzed using the gas chromatography with mass detector (GC/ MSD) and the gas chromatography with flame photo detector (GC/ FPD). Direct analysis of sulphur volatile substances is possible only rarely as they are found in the analyzed matrices (malt, beer) only in very low concentrations ( g/kg,l - ng/kg,l). Before the analysis, the analytes must be extracted from the matrix and concentrated. The modern analytical methods SPME (Solid Phase Micro Extraction), SPDE (Solid Phase Dynamic Extraction) and TDAS (Thermal Desorption Autosampler) were experimentally compared for the extraction and subsequent concentration of sulphur volatile substances. The method of gas chromatography with flame photo detector was used to determine sulphur volatile substances. Following volatile sulphur substances were monitored: dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide, carbon disulphide, ethyl sulphide, diethyl disulphide, methionol, 3-methylthiophen, ethyl thioacetate, 2-methyl-1-buthanthiol. Only metionine was detected in significant amounts in the barley samples analyzed. Not only content but also dependence on a variety and locality were studied. Further, changes in methionine, cysteine and PDMS content during malting were followed. Results proved a significant decline in these substances content depending on the kilning temperature. Three types of fibers were tested for the analyses of the selected volatile sulphur substances in beer in the SPME method. PEG - a fiber with stationary phase Carbowax, PDMS - a fiber with stationary phase polydimethylsiloxan and a combined fiber CAR/PDMS - Carboxen and polydimethylsiloxan. Carbon disulphide, methionol, dimethyl sulphide, 3-methylthiophen and diethyl disulphide were detected with this method. Content of the other analyzed volatile sulphur substances was below the limit of detection. Further was tested usage the SPDE and TDAS methods. Both methods appear to be the suitable for the determination of volatile sulphur substances in beer.
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Methionine synthase as a potential therapeutic target
Kellovská, Kristýna ; Baszczyňski, Ondřej (advisor) ; Snášel, Jan (referee)
This thesis focuses on the enzyme methionine synthase (MS), which catalyzes methylation of homocysteine to produce methionine. Two main families of these enzymes are recognized in nature - cobalamin-dependent and cobalamin-independent. These two enzymes share no sequence homology, and they also use different catalytic mechanisms, substrates and cofactors. Cobalamin-dependent MS is found in humans, whereas cobalamin-independent MS is typical for plants and fungi. In humans, the enzyme provides a connection between folate and methionine cycle - two metabolic pathways which are crucial for example for DNA synthesis and S-adenosylmethionine-dependent biological methylations. Recently, the enzyme has been recognized as a potentially promising target for the development of chemotherapeutics and antifungal drugs, mainly based on its essentiality for the proliferation of cancer cells and both viability and virulence of pathogenic fungal species.
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Vliv chráněného methioninu v krmné dávce na mléčnou produkci dojnic
BERÁNKOVÁ, Barbora
The bachelor thesis deals with the effect of limiting amino acid on dairy cow production. The research part of the thesis focuses on the digestive tract of ruminants and the importance of foregut. It also outlines the requirements for ration formulation for lactating and dry cows. The second part focuses on the indispensability of nitrogenous substances in the organism. It discusses the importance, need and evaluation of nitrogenous substances. The following chapter deals with amino acids, which are an integral part of NL The last chapter of the theoretical part focuses on methionine, on which the experiment is based. The practical part deals with the effect of protected methionine on dairy cow production and milk constituents. An average of 471 dairy cows were included in the experiment and monitoring data were collected prior to and during the administration of Smartamine M into feed ration. The results of the experiment showed the effect of Smartamine M on increasing the value of protein component in milk (statistically highly significant value (P = 0.00011).
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Metabolism of methionine and its role in cellular processes in Saccharomyces cerevisiae.
Pavelková, Eliška ; Zikánová, Blanka (advisor) ; Žáčková Suchanová, Jiřina (referee)
Methionine is a proteinogenic amino acid which can be in case of its lack synthesize by yeast, in contrast to mammals. Methionine is also indispensable for cells because it is a precursor molecule for S-adenosylmethionine (AdoMet). AdoMet participates in a biosynthesis of other molecules such as polyamines or biotin. AdoMet is a donor of a methyl group in transmethylation reactions of proteins and lipids. Due to this fact, AdoMet is involved in regulation of a variety of cellular processes. Although yeast can synthesize methionine, from energy point of view, it is more advantageous to take accept methionine from the extracellular environment. Extracellular methionine concentration also affects the expression of permeases involved in its transport into the cell and methionine biosynthesis. Intracellular availability of methionine is monitored by tRNA thiolation. Cell growth and aging is positively influenced based on the amount of thiolated tRNA. Methionine biosynthesis, translation rate and carbohydrate metabolism are negatively influenced. Recently, it has been found out that under certain conditions, lack of methionine induces non nitrogen starvation autophagy, rapidly decreases growth rate and extend life-span of cells in Saccharomyces cerevisiae. Study of the role of methionine in the cellular...
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The metabolism of amino acids in parasitic and anaerobic protists
Jakubec, Dávid ; Šuťák, Róbert (advisor) ; Hrdý, Ivan (referee)
Parasitic protists are the cause of countless pathological conditions and economic issues in many parts of the world. While being phylogenetically unrelated, they share many similarities in their approach to satisfying the essential needs. Unlike the much studied energy metabolism, amino acids utilisation pathways are rather unexplored areas. This review shows that in many cases, the parasitic life style has not had the same impact on the amino acid metabolism as it did on the energy metabolism of the protists, which is often severely reduced. Novel pathways have been found in many of the organisms in question, for the biosynthesis of amino acids deemed both essential and non-essential in humans. The arginine dihydrolase pathway found in Trichomonas and Giardia represents a complely new way of utilising the said amino acid. The metabolism of sulfur-containing amino acid has been a matter of intensive research for their non-proteogenic roles. Polyamines are organic nitrogenous compounds involved in many vital processes in the cells, including DNA replication and protein translation. The synthesis of polyamines and their derivatives is elucidated, as it is directly connected to the amino acid metabolism. Finally, the exploitation of the unique pathways described integrates the previous research with the aim...
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Study of the Selected Types of Sulphur Compounds in Beer and Brewing Materials
Mikulíková, Renata ; Ventura, Karel (referee) ; Ventura, Karel (referee) ; Čáslavský, Josef (referee) ; Márová, Ivana (advisor)
Much attention has been recently devoted to sensorially active substances affecting beer quality in the Czech Republic and worldwide. Among them, the heterocyclic and sulphur containing compounds play an important role, some of them with high sensorial activity even in extremely low concentrations. Trace amounts of these compounds, which can be frequently found in foods, participate in formation of their aroma and this effect can be generally evaluated as favorable However, in malt or beer it is true only to a limited extent and the presence of heterocyclic and sulphur containing compounds are in this respect assessed rather unfavorably. The aim of the present study was to provide a survey about of problems in the field of sulphur containing compounds in barley, malt and beer, to describe metabolic paths leading to their formation and to verify experimentally possibilities of their determination using modern analytical methods. Sulphur-containing amino acids are a natural part of barley, malt and beer and are precursors of the origin of volatile sulphur substances. The most frequently occurring sulphur amino acids, metionine, cysteine and homocysteine, were selected for analytical monitoring. The method of gas chromatography was used to determine sulphur-containing amino acids in barley, malt and beer. Prior to the analysis, sulphur-containing amino acids were derived and volatile N(O,S)-ethoxycarbonyl propyl esters were formed; they were subsequently analyzed using the gas chromatography with mass detector (GC/ MSD) and the gas chromatography with flame photo detector (GC/ FPD). Direct analysis of sulphur volatile substances is possible only rarely as they are found in the analyzed matrices (malt, beer) only in very low concentrations ( g/kg,l - ng/kg,l). Before the analysis, the analytes must be extracted from the matrix and concentrated. The modern analytical methods SPME (Solid Phase Micro Extraction), SPDE (Solid Phase Dynamic Extraction) and TDAS (Thermal Desorption Autosampler) were experimentally compared for the extraction and subsequent concentration of sulphur volatile substances. The method of gas chromatography with flame photo detector was used to determine sulphur volatile substances. Following volatile sulphur substances were monitored: dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide, carbon disulphide, ethyl sulphide, diethyl disulphide, methionol, 3-methylthiophen, ethyl thioacetate, 2-methyl-1-buthanthiol. Only metionine was detected in significant amounts in the barley samples analyzed. Not only content but also dependence on a variety and locality were studied. Further, changes in methionine, cysteine and PDMS content during malting were followed. Results proved a significant decline in these substances content depending on the kilning temperature. Three types of fibers were tested for the analyses of the selected volatile sulphur substances in beer in the SPME method. PEG - a fiber with stationary phase Carbowax, PDMS - a fiber with stationary phase polydimethylsiloxan and a combined fiber CAR/PDMS - Carboxen and polydimethylsiloxan. Carbon disulphide, methionol, dimethyl sulphide, 3-methylthiophen and diethyl disulphide were detected with this method. Content of the other analyzed volatile sulphur substances was below the limit of detection. Further was tested usage the SPDE and TDAS methods. Both methods appear to be the suitable for the determination of volatile sulphur substances in beer.
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