Description et caractérisation de la diversité microbienne durant l'élaboration du vin : Interactions et équilibres – Relation avec la qualité du Vin

Sur le raisin coexiste, dans un système organisé, une grande variété de microorganismes, dont une partie comprend les principales espèces utiles à la vinification. Après le foulage, les interactions entre les levures et les bactéries assurent les fermentations alcoolique et malolactique et, après le sulfitage, les suivis des espèces résiduelles suggèrent que ces interactions persistent durant la période d'élevage du vin ce qui peut conduire à une altération des vins si des espèces comme la levure Brettanomyces bruxellensis persistent et se multiplient. La compréhension de ces évolutions implique une vision globale de la diversité microbienne. Chaque opération technologique et chaque processus fermentaire influence la diversité des espèces et des souches présentes. Globalement, le système se simplifie car le vin devient de plus en plus carencé et toxiques pour les micro-organismes. O. oeni et B. bruxellensis sont les espèces les plus résistantes. Des collections de ces espèces isolées de vin ont été étudiées. La diversité intraspécifique est révélée par des études phénotypiques et génétiques pour la première. La variabilité dans la production des phénols volatils, qui altèrent le vin est démontrée chez la seconde. ABSTRACT : On the grape, a large variety of micro-organisms coexist in an organized system including the principal species useful for winemaking. After pressing, interactions between yeasts and bacteria ensure alcoholic fermentation and fermentations. After sulphiting, the evolution of residual species suggests that interactions persist during the period of ageing, which can lead to a wine spoilage if species as the yeast Brettanomyces bruxellensis persist. The understanding of theses evolutions is necessary and needs a global view of the microbial diversity. Each technological operation and fermentative process influences the species and strains diversity. The system is gradually simplified because the wine becomes more and more deprived and toxic. Among the most resistant species, there are O. oeni and B. bruxellensis. Strains collections have been constituted for these species. The instraspecific diversity is shown by phenotypic and genetics studies in the first one. The variability in volatile phenols production, which spoils wine, is shown in the second

Comparison and Coupling of Algorithms for Collisions, contact and friction in rigid multi-body simulations.

International audienceNumerous works in computational mechanics are dedicated to multi-body systems. This leads to the use of various methods to simulate the static or dynamic evolution of complex systems. The case of dense multi-contact assemblies is one of the more complex one: the problem have often a large number of unknown and have a infinity of solution due to the definition of the matrix of the system. Moreover this problem become harder when friction or more complex laws are introduced in the system. Thus we need fast and robust solvers to perform mechanical studies. These performances can be increased when the special problem structure is considered (sparse matrices, block structured problem). Our work is based on the Non Smooth Contact Dynamic framework introduced by Moreau. The method uses a time-stepping integrator without explicit event-handling procedure and an unilateral contact impact formulation associated to Coulomb's friction. In this paper we use and compare different iterative algorithms such as Gauss-Seidel, projected conjugate gradient and direct ones as Lemke and Quadratic programming solvers. The efficiency of the methods is compared in terms of complexity, convergence criterion and of CPU time. To illustrate the results, we focus on granular assemblies. 3D frictional contact simulations are performed with ConF&TiS and the Numerics library of the siconos project

Changes in Grape Maturity Induced by Spraying Ethanol

Three different ethanol solutions were sprayed onto Cabernet Sauvignon (Vitis vinifera L.) clusters during the ripening period: 2.5, 5 and 10% by volume in water. Controls were sprayed with water alone. Three different times of spraying were also tested: 8, 10 and 13 weeks post-flowering. One of the observed changes was a lower titratable acidity in grape samples at harvest, when the clusters were sprayed with ethanol at 10 weeks, in comparison with controls. The wines made with grapes treated with ethanol after mid-veraison, had higher ODs at 520 nm than did the controls. This may due to a combined effect of red pigment levels and acidity. In addition, following malolactic fermentation, the acidity levels of wines made with ethanoltreated grapes were slightly higher than those made with the control grapes. Spraying ethanol at 13 weeks post-flowering increased the berry weight by 10% at harvest without decreasing the °Brix value. The corresponding wines had similar degrees of alcohol. This observation was made for the first time in 2001

High intraspecific variation of the cell surface physico-chemical and bioadhesion properties in Brettanomyces bruxellensis

Brettanomyces bruxellensis is the most damaging spoilage yeast in the wine industry because of its negative impact on the wine organoleptic qualities. The strain persistence in cellars over several years associated with recurrent wine contamination suggest specific properties to persist and survive in the environment through bioadhesion phenomena. In this work, the physico-chemical surface properties, morphology and ability to adhere to stainless steel were studied both on synthetic medium and on wine. More than 50 strains representative of the genetic diversity of the species were considered. Microscopy techniques made it possible to highlight a high morphological diversity of the cells with the presence of pseudohyphae forms for some genetic groups. Analysis of the physico-chemical properties of the cell surface reveals contrasting behaviors: most of the strains display a negative surface charge and hydrophilic behavior while the Beer 1 genetic group has a hydrophobic behavior. All strains showed bioadhesion abilities on stainless steel after only 3 h with differences in the concentration of bioadhered cells ranging from 2.2 × 102 cell/cm2 to 7.6 × 106 cell/cm2. Finally, our results show high variability of the bioadhesion properties, the first step in the biofilm formation, according to the genetic group with the most marked bioadhesion capacity for the beer group. © 2023 The Author

Injection de concentrés plaquettaires et régénération tendineuse : modèle animal

peer reviewedIntroduction : La régénération tendineuse en traumatologie du sport demeure un processus actuellement difficile à gérer et de nouvelles voies thérapeutiques sont en cours d’exploration. La littérature récente fait état d’effets bénéfiques sur la régénération tendineuse de concentrés plaquettaires (platelet-rich plasma ou PRP), administrés in situ, dus au relargage de facteurs de croissance par activation des plaquettes et à leur activité stimulante au cours de la cicatrisation. Dès lors, nous avons souhaité tester l’effet bénéfique de ce traitement sur des rats préalablement lésés au niveau de leur tendon d’Achille. Matériel et Méthode : Une section unilatérale du tendon d’Achille a été réalisée chez 60 rats Sprague Dawley adultes. De ces 60 rats, 30 ont subi une cicatrisation naturelle (rats contrôles) et 30 rats ont bénéficié d’une injection in situ de PRP le jour de la lésion. Diverses études biomécaniques, biochimiques et histologiques ont été réalisées sur ces tendons d’Achille en cours de cicatrisation à respectivement J5, J15 et J30 après lésion. Dix rats supplémentaires ont servi de témoins sains (sans lésion tendineuse). L’étude biomécanique appréciait la résistance maximale des tendons à la traction à l’aide de mors type « cryo-jaws ». L’étude histologique évaluait l’évolution cellulaire pendant la phase de cicatrisation. L’analyse transcriptomique étudiait l’expression de gènes codant pour le collagène de type III, les métalloprotéases matricielles (MMP-9) et la ténomoduline (TNMD), ainsi qu’un dosage d’hydroxyproline permettant d’évaluer la quantité de collagène présente dans le tendon au cours de la cicatrisation. Résultats : L’étude biomécanique démontre la meilleure résistance des tendons traités avec du PRP par rapport aux tendons contrôles à J5 (+19%), J15 (+30%) et significativement à J30 (+43%). L’étude histologique suggère qu’une injection de PRP stimule la prolifération cellulaire, favorise l’organisation tissulaire, stimule l’angiogenèse et la réorganisation architectural du collagène. L’étude biochimique ne permet pas d’expliquer les effets bénéfiques puisqu’il n’y a pas de différence dans l’expression des gènes des différentes molécules matricielles (collagène de type III, MMP-9 et TNMD) ni dans la quantité d’hydroxyproline qui s’accroit au cours du temps de la cicatrisation de façon similaire dans les deux groupes. Conclusion : L’injection de PRP améliore et accélère la cicatrisation tendineuse et augmente la résistance aux contraintes mécaniques du tendon en cours de cicatrisation

Racking are key stages for the microbial stabilization of wines

This study aims to understand the effect on micro-organism of racking when the wine is aged in barrels. According to the kind of micro-organism, the effects are different. Bacteria are stimulated by oxygen and their population increases. Yeasts are concentrated to the bottom of the barrel. Between two successive racking a yeast population gradient was established. Yeast cells which are larger and heavier than bacteria cells and they are deposited on the barrel bottom with other wine micro-particles. In some cases, the yeast population at the bottom was more than thousand times than at the wine surface. Moreover, the species identified at different heights in the barrel were different. Saccharomyces cerevisiae was the main yeast detected at the surface, whereas Brettanomyces bruxellensis was the main yeast lees. After racking yeast population decreases because they are eliminated with the lees during the operation. Among them, Brettanomyces bruxellensis was the majority. Since they are able to produce volatile phenols, their preservation in the barrel can lead to the alteration of the wine. Indeed, the ability of the lees to produce volatile phenols was clearly established. The importance of regular racking for microbial wine stabilization is evident. The risks of «sur lies» wine aging and sticking’s operations are underlined

Description et caractérisation de la diversité microbienne durant l'élaboration du vin (interactions et équilibres, relations avec la qualité du vin)

On the grape, a large variety of micro-organisms coexist in an organized system including the principal species useful for winemaking. After pressing, interactions ensure alcoholic fermentation and fermentations. After sulphiting, the evolution of residual species suggests that interactions persist. Their understanding is necessary and needs a global view of the microbial diversity. Each technological operation and fermentative process influences this diversity. The system is gradually simplified because the wine becomes more and more deprived and toxic. Among the most resistant species, there are O. oeni and B. bruxellensis. Strains collections have been constituted for these species. The instraspecific diversity is shown by phenotypic and genetics studies in the first one. The variability in volatile phenols production, which spoils wine, is shown in the secondTOULOUSE-ENSIACET (315552325) / SudocVILLENAVE D'ORNON-Bib. ISVV (335502201) / SudocSudocFranceF

Comparison of Algorithms for collisions, contact and friction in view of Real-time applications

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3D frictional contact and impact multibody dynamics. A comparison of algorithms suitable for real-time applications

International audienceDuring the last decade Virtual Reality has benefited of numerous works dedicated to the modeling and the simulation of multibody systems. Even if a large set of methods are already used by the community of computer graphics and virtual reality, some progresses need still to be made to bridge the gap between accurate mechanical simulation and efficient simulations in real-time of realistic systems. Particularly, the problem of the three dimensional frictional contact with impacts is a key point for the applications with haptic feedback. The work aims at adapting the outstanding methods in computational mechanics to the real-time constraints induced by Virtual Reality. For efficiency reasons, our work is based on the Non Smooth Contact Dynamics (NSCD) framework introduced by Moreau (1988). Two major advantages of the method can be exhibited for the real-time context: the method uses a time-stepping numerical scheme without explicit event-handling procedure and an unilateral contact impact formulation associated with the 3D Coulomb's friction law. In the present paper, we use and compare different iterative algorithms (Non Smooth Gauss-Seidel, projected conjugate gradient, the PATH solver) for complementarity problems with a direct one (Lemke). The efficiency of the methods is compared in terms of complexity, of quality ratio between visual feed-back of solution and convergence criterion and of CPU time keeping in mind the real-time constraint

Yeast and bacteria analysis of grape, wine and cellar equipments by PCR-DGGE

Aims: Microorganisms play an important role in winemaking. Most of their metabolisms are beneficial to the wine quality but several species have spoilage effects. Microbiological knowledge are crucial for improving species and strains identification and avoiding contamination by spoilage agents. Our objective was to follow wine microbial consortia at each stage of the process from grapes to bottles, and also on cellar equipment surface: barrels for the yeast analysis and tanks for the bacteria analysis. Methods and results: For a global microbial monitoring, molecular tools are particularly efficient. We chose the PCR-DGGE for direct analyses without cultivation step. We used the rpoΒ gene as target for the bacteria, and the 26S rRNA gene for the yeast. Species inventories were made during the whole winemaking process, which had never been done before. Conclusion: From the grape surface to storage in bottles, the microbial diversity decreased. Only the most resistant species were able to survive to the ethanol, SO2, low oxygen and low pH constraints. Among them, Pediococcus parvulus for the bacteria and Brettanomyces bruxellensis for the yeast were the most resistant. Significance and impact of study: The use of a molecular method independent of the culture stage of the microorganisms like the PCRDGGE has allowed to have a more exhaustive vision of the diversity of the bacteria and yeasts species and to follow their evolution during the winemaking and in the cellar environment . These follow-ups could be extended to other estates in order to study the causes and the consequences of certain variations. The detection of these two prejudicial species was an argument for the PCR-DGGE approach in wine microbial studies