Modulation de la transition respiro-fermentaire chez Saccharomyces cerevisiae par l'oléate : analyse cinétique et métabolique en culture continue sur substrats mixtes

L'objectif de ce travail est d'étudier la transition respiro-fermentaire chez Saccharomyces cerevisiae et de déterminer l'étape ou les étapes contrôlant ce processus, à partir d'une approche originale de génie microbiologique basée sur l'utilisation de chémostat sur substrats mixtes. Dans un premier temps, l'analyse bibliographique a orienté notre travail vers l'étude du rôle du transport du carbone du cytosol vers la mitochondrie. Pour déterminer si ce transport exerce un contrôle sur la bascule métabolique, nous avons mis en place une stratégie consistant à introduire en chémostat sous limitation glucose en mode oxydatif une perturbation métabolique ciblée ( présence de co-substrat, modification génétique) et à analyser les conséquences de cette perturbation sur la bascule métabolique étudiée. L'oléate a été un des co-substrats testés dans ce travail car il est connu pour stimuler les enzymes impliquées dans le transport du carbone à travers la membrane mitochondriale. La transition respiro-fermentaire a donc été quantifiée en chémostat glucose seul et en chémostat glucose/oléate. En présence d'oléate, il a été observé un retard dans l'apparition de la bascule métabolique et une redirection du flux carboné de la voie fermentaire vers la voie oxydative. Ce résultat marquant met en évidence une diminution de la transition respiro-fermentaire en présence d'oléate et constitue un des rares succès reporté dans la littérature de réduction de l'effet Crabtree. L'action de l'oléate a été approfondie et discutée au cours de ce travail.\ud ____________________________________________________________This work aims to study the respiro-fermentative transition in Saccharomcyces cerevisiae and to determine the controlling step(s) involved in this process, by using an original approach of microbiological engineering based on co-substrate chemostat cultivations. Based on the literature analysis, we focused our work on investigating the importance of the carbon transport from cytosol to michondria in the onset of the metabolic shift. To determine whether this transport exerts a control on the metabolic change, a strategy was implemented consisting in introducing, during oxidative glucose limited chemostat, a specific metabolic perturbation ( addition of co-substrate, genetic modification) and in analysing the consequences of such a perturbation on the studied metabolic event. The oleic acid was one of the co-substrates tested in this work; this fatty acid is indeed know to simulte enzymes implied in the carbon transport between the different cell compartments. The metabolic transition was then studied in sole glucose chemostat and in glucose/oleic acid chemostat. In the presence of oleic acid, a delay in the onset of the metabolic shift and a redirection of the carbon flux from the reductive pathway were observed. This important result shows a modulation in the respiro -fermentative transition in presence of oleic acid and constitutes one of the few success reported in the literature of reduction in the Crabtree effect. the action of the oleic acid was further investigated and discussed throughout this work

Unravelling copper effect on the production of varietal thiols during Colombard and Gros Manseng grape juices fermentation by Saccharomyces cerevisiae

Nowadays the rapidly increasing organic vineyard management with the utilization of copper as sole fungal control pesticide against downy mildew raises once again the question of copper impact on varietal thiols in wine. For this purpose, Colombard and Gros Manseng grape juices were fermented under different copper levels (from 0.2 to 3.88  mg/l) to mimic the consequences in must of organic practices. The consumption of thiol precursors and the release of varietal thiols (both free and oxidized forms of 3-sulfanylhexanol and 3-sulfanylhexyl acetate) were monitored by LC–MS/MS. It was found that the highest copper level (3.6 and 3.88  mg/l for Colombard and Gros Manseng respectively) significantly increased yeast consumption of precursors (by 9.0 and 7.6% for Colombard and Gros Manseng respectively). For both grape varieties, free thiol content in wine significantly decreased (by 84 and 47% for Colombard and Gros Manseng respectively) with the increase of copper in the starting must as already described in the literature. However, the total thiol content produced throughout fermentation was constant regardless of copper conditions for the Colombard must, meaning that the effect of copper was only oxidative for this variety. Meanwhile, in Gros Manseng fermentation, the total thiol content increased along with copper content, resulting in an increase up to 90%; this suggests that copper may modify the regulation of the production pathways of varietal thiols, also underlining the key role of oxidation. These results complement our knowledge on copper effect during thiol-oriented fermentation and the importance of considering the total thiol production (reduced+oxidized) to better understand the effect of studied parameters and differenciate chemical from biological effects

GERENCIAMENTO DE RESÍDUOS SÓLIDOS DE UMA INDÚSTRIA GRÁFICA COM ENFOQUE EM PRODUÇÃO MAIS LIMPA (P+L): ESTUDO DE CASO NO ESPÍRITO SANTO

No segmento industrial gráfico, dentre os impactos ambientais causados pela geração de poluição, a geração de resíduos sólidos torna-se fator preocupante, dado a relação de sua geração com o desperdício de matérias-primas, aumento de custos de produção e reduzida eficiência no processo industrial, o que exerce influência sobre a valoração do produto final, sobre a rentabilidade econômica destes produtos e a competitividade da indústria no mercado. Desta forma, a otimização da produção industrial é fator decisivo para competitividade e permanência no mercado. A redução da geração de poluição, mitigação dos impactos ambientais e a otimização de processos, em sua forma preventiva, está ancorada na Política Nacional de Resíduos Sólidos, Lei nº 12.305/2010. O gerenciamento de resíduos sólidos industriais pode se tornar estratégia corporativa para prevenção da geração de poluição e que traduz-se em ações de otimização da produção e melhoria contínua, o que relaciona-se a metodologia de Produção Mais Limpa (P+L). Assim, o objetivo desta pesquisa foi diagnosticar o gerenciamento de resíduos sólidos com enfoque nas premissas da metodologia de P+L em uma indústria gráfica e implementar um Programa de Gerenciamento de Resíduos Sólidos (PGRS) visando a otimização da produção industrial, equilíbrio sustentável dos processos e redução da geração de resíduos sólidos. Constatou-se que a gráfica em estudo teve a oportunidade de entender a importância do PGRS, da adoção de valores ecoeficientes e valor funcional ao fluxo do processo industrial, consolidando, portanto, as técnicas implementadas. A contribuição do PGRS pode ser observada pelo desempenho positivo das ações implementadas, que resultou num equilíbrio entre o consumo de matérias-primas e a geração de resíduos sólidos, possibilitando agregar valor ao produto final. A sinergia das ações implementadas, pautadas na integração do PGRS e P+L, possibilitou a melhoria do desempenho ambiental da gráfica, interferindo positivamente no desempenho operacional com a adequada operacionalização industrial. Os resultados apresentados sugerem que as indústrias do segmento gráfico e demais setores industriais explorem a metodologia adotada, adotando o PGRS como ferramenta de um sistema gestão ambiental integrado

Impact of phytosterol addition on fermentation progress and volatile compounds synthesis during alcoholic fermentation in synthetic and natural grape musts

Lipid nutrition is an important factor for yeast during alcoholic fermentation. Although recent research reports have revisited the role of sterols during alcoholic fermentation, our knowledge of lipids assimilation and volatile compound biogenesis remains partial. This study aimed to find out more about the impact of grape must phytosterol content on fermentative kinetics, nitrogen assimilation by yeast and fermentative aroma synthesis. To that end, experimental fermentations were performed in synthetic and Chardonnay musts supplemented with different phytosterol concentrations (0, 1, 3 and 5 mg/L). Sterols addition significantly increased the maximum CO2 production rate while reducing fermentation duration. This can be explained by higher nitrogen assimilation by yeast due to sterols, which leads to higher yeast growth and better viability at the end of the fermentation process. Regarding the aromatic profile, sterol addition also significantly increased acetate esters, ethyl esters, fusel alcohols and medium-chain fatty acids production. These new advances highlight the major role of phytosterols in fermentation control and wine aroma profile

Fermentation alcoolique en œnologie : du suivi en ligne à l'optimisation multicritères

Fermentation alcoolique en œnologie : du suivi en ligne à l'optimisation multicritères . 6. Rencontre ESOF : "Transformation numérique des agrochaînes

Study and Modeling of the Evolution of Gas − Liquid Partitioning of Hydrogen Sul fi de in Model Solutions Simulating Winemaking Fermentations

The knowledge of gas-liquid partitioning of aroma compounds during winemaking fermentation could allow optimization of fermentation management, maximizing concentrations of positive markers of aroma and minimizing formation of molecules, such as hydrogen sulfide (H2S), responsible for defects. In this study, the effect of the main fermentation parameters on the gas-liquid partition coefficients (Ki) of H2S was assessed. The K-i for this highly volatile sulfur compound was measured in water by an original semistatic method developed in this work for the determination of gas-liquid partitioning. This novel method was validated and then used to determine the K-i of H2S in synthetic media simulating must, fermenting musts at various steps of the fermentation process, and wine. K-i values were found to be mainly dependent on the temperature but also varied with the composition of the medium, especially with the glucose concentration. Finally, a model was developed to quantify the gas-liquid partitioning of H2S in synthetic media simulating must to wine. This model allowed a very accurate prediction of the partition coefficient of H2S: the difference between observed and predicted values never exceeded 4%

Modulation de la transition respiro-fermentaire chez Saccharomyces cerevisiae par l'oléate (analyse cinétique et métabolique en culture continue sur substrats mixtes)

TOULOUSE-INSA (315552106) / SudocSudocFranceF

Maitrise des intrants lors de la fermentation œnologique

Maitrise des intrants lors de la fermentation œnologique. SITEV