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Barley Proteomic Studies Related to Beer Production
Benkovská, Dagmar ; Márová, Ivana (oponent) ; Ehrenbergerová, Jaroslava (oponent) ; Zdráhal, Zbyněk (oponent) ; Bobáľová, Janette (vedoucí práce)
This work is focused on barley proteomic studies in relation to the beer production. Barley belongs between the most important crops in the world and its greatest use is for malting purposes, most commonly for the brewing industry. Studies of barley proteins during malting and brewing provide information about changes in protein composition or their post translational modifications. Since the protein composition and their modifications are essential for the quality of malt and beer, barley proteomic studies have a potential to improve the malting and brewing process. The main goal of this thesis is to investigate barley water-soluble proteins and their changes that occur during the malting and brewing process. The differences in protein composition were investigated using gel electrophoresis, reversed phase and size exclusion liquid chromatography, and MALDI-TOF mass spectrometry. The amount of some proteins is increasing and some new proteins are created in the germinated grain during the malting process. Contrary, many proteins are decomposed during the brewing process due to the high temperature and enzymatic activity of some proteases. Only some proteins belonging to the family of pathogenesis related proteins resist these harsh conditions and pass into the beer where they can influence several important quality properties. Furthermore, various barley varieties and their differences were investigated. Varieties allowed for the production of certified Czech beer were compared to one variety with well proven malting properties and one non-malting barley variety. In addition, alcohol soluble barley proteins and their changes during the malting process were investigated as well. A special attention was paid to selected post-translational modifications of proteins, namely glycosylations. Non-enzymatically glycosylated barley proteins (or glycated proteins) are formed during the malting process considering the large amount of glucose released from the starch degradation, and influence the protein stability as well as the beer quality, especially foaming properties. Enzymatic N-glycosylation represents the most frequently studied post translational modification in plants because glycoproteins play a key role in various biological functions. Since glycoproteins are often present in a small amount, their enrichment from a complex mixture is required for their analysis. Lectin concanavalin A affinity chromatography was used for barley glycoproteins investigation. Moreover, the analysis of the carbohydrate part of glycoproteins was optimized. This doctoral thesis brings important information about barley proteins, their modifications and analysis that are useful for further studies.
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