No description available.

The detection and quantitation of substances using analytical techniques is an important area in many fields. Accuracy,dependability, reproducibility, specificity and stability of the techniques used are all important. The first three parameters are largely operator dependent, however, specificity and stability of the components of the tests also play a part. The specificity of analysis may be determined chemically or biologically by using enzymes, immunological reagents or receptors of some sort. However, biological molecules are often unstable in purified, isolated forms and must be stabilised in some way to retain activity. The work reported here attempts to increase the knowledge of enzyme stabilisation, using the enzyme alcohol oxidase as a test enzyme. This enzyme was used in : (i) A manual assay for ethanol determination. (ii) An automated assay using both soluble and immobilised enzyme in segmented flow and flow injection analysis. (iii) A dry phase stabilised enzyme based test for ethanol in saliva. During the course of the work a method for stabilising the enzyme was discovered. This has been applied to a number of other enzyme systems, successfully stabilising them in most cases. This work forms the basis of a patent application for enzyme stabilisation. A novel detection system allowing semi-quantitative results to be obtained, using stabilised dry phase technology has also been discovered. A second patent application has been filed and the system has been applied to analytes measured by oxidase enzymes. The final area of investigation was to develop an enzymic assay for diacetyl. This substance is a contaminant in beer and as such requires accurate detection at low levels. The purification and characterisation of diacetyl reductase from a new source, (chicken liver) enabled various assay formats to be investigated. These included dye linked assays and enzyme amplified recycling assays to determine diacetyl in aqueous samples.

Thesis--Helsingfors. / "Literaturverzeichnis": p. [71]-74.

No description available.

The concentration of diacetyl in the fermenting process of beer is important to control as it is both a measure of the quality of the beer and yeast viability. Presently there is no on line method for monitoring diacetyl levels during beer production, which can result in submitting the beer to a longer high temperature diacetyl degradation period than necessary. This is detrimental to the yeast and increases the time of the overall process. The ability to continuously monitor diacetyl levels on line would provide a decided advantage in control of the fermentation and maturation of the beer, two important factors impacting production quality and cost. The purpose of this project is to design a biosensor that will measure diacetyl levels on line, thereby providing a profile of diacetyl concentrations during beer production. This will lead to increasing not only the production rate, but the quality and consistency of the final product and can serve as a foundation for future improvements in yeast management in general. / The initial goal of the project is to evaluate existing biosensor technology in relation to its application in the beer fermentation process. The second is to design a biosensor which will measure diacetyl levels and surmount existing biosensor disadvantages based on the information collected in the observation process. The last objective is to construct a prototype in order to test this design. The combined results of this study will be of value to the brewing industry specifically and help expand the role biosensors play in introducing new more effective methods into the food processing industry.

No description available.

Diacetyl (2,3-butanedione) is an important flavour active, oxidative compound that has significant impact on cellular health as well as financial impact in industrial fermentations. The presence of diacetyl in certain fermented beverages, such as beer, results in an unpleasant butterscotch-like flavour and its concentration needs to be reduced by yeast to below the taste threshold prior to filtration and packaging. This results in significant process inefficiency. Furthermore, diacetyl negatively impacts cellular health and has been associated with neurodegenerative diseases and general cell aging amongst others. The reduction of this compound is therefore essential for cellular health. / Several yeast cell enzymatic mechanisms responsible for diacetyl reduction were identified and characterised, including Old Yellow Enzyme (OYE) isoforms and D-Arabinose Dehydrogenase (ARA1). OYE isoforms displayed different micromolar affinities and catalytic turnover rates for diacetyl and catalysed diacetyl reduction in a biphasic manner. ARA1 catalysed diacetyl reduction in a monophasic manner with a millimolar Michaelis constant. / Knowledge gained in these studies was applied in investigations of diacetyl production and reduction in industrial brewing operations and the enzymatic systems further exploited for the development of a novel enzyme based assay to determine diacetyl concentrations in beer samples. Concentrations as low as 0.2 muM were detectable with high repeatability.

No description available.

Moët & Chandon est le leader mondial incontesté dans le secteur des vins mousseux de haute qualité. La sélection des différentes gammes de vins de qualité se fait sur la base de la dégustation de vin, après la fermentation malolactique par la dégustation des jurys d'experts. Une partie importante du volume vinifié ne peut être classé parmi les vins les plus qualitatifs à cause d'un caractère organoleptique appelé «trait lactique». Cette caractéristique est due à la formation de métabolites volatils au cours de la fermentation du vin en particulier diacétyle, acétoïne et de 2,3-pentanedione. Le diacétyle, également connu sous le nom de 2,3-butanedione, est le principal marqueur associé à l'apparition de notes beurrées. Moët & Chandon souhaite commencer une thèse pour contrôler l'apparition de trait lactique dans ses vins de bases. Bien que la production de diacétyle se produit à la fois pendant la fermentation alcoolique (FA) et la fermentation malolactique, la thèse se concentrera sur la gestion de la FA. Une approche multi-factorielle basée à la fois sur l'ingénierie microbiologique et chimique sera mis en œuvre. Dans un premier temps, le travail visera à mieux comprendre le fonctionnement et la régulation des voies métaboliques impliquées dans la formation de diacétyle. De cette information, nous allons développer des stratégies de contrôle de la fermentation afin de minimiser le caractère lactique de vins. Dans ce travail, le rôle et l'impact des paramètres de fermentation sera particulièrement évalué. Le projet commencera par la mise en œuvre des outils d'analyse nécessaires au suivi des marqueurs de trait lactique (diacétyle, acétoïne, 2,3-pentanedione, ...). Deuxièmement, sur un support synthétique, le projet permettra de caractériser le processus de fermentation. Surtout, les équilibres azotés seront contrôlés et les cinétiques de synthèse des composés responsables de trait d'arôme lactique seront déterminées. Une étude de l'impact des acides aminés précurseurs permettra de mieux comprendre le rôle du métabolisme de l'azote. Enfin, l'étude de l'effet de divers facteurs tels que la nature des substances nutritives, température de fermentation et l'apport en oxygène devrait conduire à l'élaboration de stratégies de contrôle rendant possible la diminution du caractère lactique dans les vins destinés à la fermentation secondaire. Dans la dernière partie de projet, les différentes stratégies développées sur moûts synthétiques seront évaluées dans des conditions de vinification réelles. / Champagne company Moët & Chandon is the undisputed worldwide leader in the high quality sparkling wines sector. The selection of different ranges of quality wine is done on the basis of the wine tasting, after malolactic fermentation by tasting expert juries. A significant part of the vinified volume cannot be valued among the most qualitative wines because of a particular feature called « lactic trait ». This trait is attributable to the formation of volatile metabolites during wine fermentation particularly diacetyl, acetoin and 2,3-pentanedione. Diacetyl, also known as 2,3-butanedione, is the main marker associated with the appearance of milky-buttery notes. Champagne company Moët & Chandon wishes to initiate a thesis to control the onset of lactic trait in its wines. Although the production of diacetyl occurs both during alcoholic fermentation (AF) and malolactic fermentation, the thesis will focus on the management of AF. A multi-factorial approach based on both microbiological and chemical engineering will be implemented. At first, the work will aim to better understand the functioning and regulation of metabolic pathways involved in the formation of diacetyl. From this information, we will develop some strategies of fermentation control to minimize the lactic trait of wines. In this work, the role of fermentation parameters will be particularly evaluated. The project will start by the implementation of the analytical tools needed to monitor markers of lactic trait (diacetyl, acetoin, 2,3-pentanedione, ...). Secondly, on synthetic media, the project will allow to characterize the fermentation process. Especially, nitrogen balances will be performed and the kinetics of synthesis of the aroma compounds responsible of lactic trait will be determined. A study of the impact of the precursor amino acids will enable to better understand the role of the nitrogen metabolism. Finally, the study of the effect of various factors such as the nature of nitrogen nutrients, fermentation temperature and oxygen intake should lead to the development of control strategies making possible the decrease of the lactic trait in wines intended for the secondary fermentation. In the final part of the work, the different strategies developed on synthetic must will be assessed in real winemaking conditions.

The dental community has a broad understanding of how traditional combustible cigarettes affect the oral cavity of the dental patient but there is little research available on the effects that e-cigarettes have on the patient’s dental health. Vaping products have been marketed as a healthier option over traditional combustible cigarettes. Since they were first introduced in 2003, very little research has been performed to understand their dental implications. This project was executed to investigate the chemicals associated with these vaping products and how they possibly contribute to the progression of periodontal disease. This research project was conducted with the contribution of 23 participants who confirmed the usage of vaping products via an anonymous online survey. Participants were dental patients of record at the University of Tennessee College of Dentistry. The data collected was analyzed and it was determined that there is a positive correlation between the use of e-cigarettes and the prevalence of periodontal disease.