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B. bruxellensis tauchte ab den 1950er Jahren in den Verzeichnissen von Most- und Weinhefen auf und wurde alsbald fur das ungeniesbar werden von Wein verantwortlich gemacht. Sehr viel spater wurden die von diesen Hefen produzierten fluchtigen Phenole als Ursache der geschmacklichen Verschlechterung ausgemacht. Ihr Vorhandensein ist ein Thema, das an Bedeutung gewinnt, insbesondere bei der Fassreifung. Die Sulfitzugabe ist ein ideales Mittel zu ihrer Beseitigung, das allerdings nicht immer ausreicht. B. bruxellensis ist besonders gut an Wein angepasst, und bereitet nun Winzern und Mikrobiologen Kopfzerbrechen.

Aims: The aim of this study was to develop a colorimetric test to determine Oenococcus carbohydrate consumption profile.Methods and results: A semi-defined growth medium which enabled efficient bacterial growth and medium acidification in the presence of glucose was developed. The inoculum size and the presence of citrate in the medium were optimized. Acidification of the medium was revealed by adding bromocresol green and was shown to be perfectly correlated with D-glucose, D-fructose, L-arabinose, D-xylose, L-rhamnose, D-cellobiose or D-trehalose consumption by 23 distinct O. oeni strains and one O. kitaharae strain (confirmed with HPLC analysis).Significance and impact of the study: Efficient bacterial growth is essential before malic acid degradation occurs in wine. The method developed here will facilitate the comparison of numerous O. oeni strains and their ability to grow by using the various carbohydrates present in wine prior to malolactic fermentation.

Aims: This work reviews the latest knowledge concerning the role of Brettanomyces bruxellensis in red wine alteration.Results and conclusion: The origin of this yeast species and its place in the wine microbial consortium are discussed as well as microbial equilibriums with the other species, notably Saccharomyces cerevisiae and lactic acid bacteria. As a consequence, fermentations are described as key steps in Brettanomyces development management. Furthermore, the influence of ageing through the use of traditional winemaking practices is explained.Significance and impact of study: Finally, this paper emphases the need for a better understanding of chemical and microbial analysis together in order to better control this undesirable yeast and prevent the production of volatile phenols.

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.

Botrytis-affected wines are microbiologically unstable. Fermentation can occasionally occur during maturing time or bottle-ageing. However, wines which undergo refermentations seem to be free of yeasts. This work deals with microbial aspects and ecology of wines during alcoholic fermentation, then during refermentation. Yeast survival after stopping the alcoholic fermentation by sulphur dioxide addition is considered. Results suggest that most yeasts could survive in sweet wine under the viable but non-culturable (VBNC) state. The increase of acetaldehyde these wines in response to sulfiting is known for long time but not the conditions of its formation. In this work we show that it is probably the key of the refermentation phenomenon, through the increase of the binding power. During maturing successive cycles occur: acetaldehyde consumption, revival, death and/or new enter into VBNC state accompanied by acetaldehyde formation which increased the binding power. Then as molecular SO2 became too low, yeasts could start a new fermentation. In this work, an ecology study was also undertaken, to understand the effect of SO2 on yeast biodiversity. Most of the fermentative yeasts could survive especially Saccharomyces cerevisiae and Zygosaccharomyces sp., together with other yeast genera. In regard to Saccharomyces cerevisiae only which is often responsible for the refermentation phenomenon, this work concluded on the decrease of strain diversity to only one or two strains, in spite of the high degree of diversity during the alcoholic fermentation. The intra-species selection probably conducted to sulfite-resistant strains.

Des vins blancs liquoreux ont été mutés par traitement aux hautes pressions. La fermentation alcoolique est complètement et définitivement arrêtée lorsque les vins sont traités à 3000- 3500 bars pendant 10 min. Il ne reste plus aucune levure viable. Le traitement n'a aucun effet majeur sur la constitution du vin, au moins en ce qui concerne ses caractéristiques principales. Seule la couleur est légèrement modifiée. Les vins ainsi traités doivent être protégés contre l'oxydation. Les qualités organoleptiques ne sont pas modifiées.Ce traitement doit être évalué à plus grande échelle afin de connaÎtre ses effets sur le vieillissement de différents types de vins.

La lyse de Leuconostoc oenos a été étudiée en suspension dans l'eau et dans une solution synthétique (pH 3,5; alcool 11 % v/v, acide tartrique 4 g/l). Elle a été mesurée par deux méthodes basées sur la libération de constituants cellulaires (mesure à 210 mm) et sur la diminution de l'opacité de la solution (mesure à 600 nm). Les cellules en phase de croissance exponentielle se lysent plus facilement que les cellules prélevées pendant les autres phases du cycle cellulaire.L'éthanol dans le milieu de suspension augmente la lyse de cellules cultivées dans le milieu standard. Par contre, le phénomène est plus limité dans la solution acide et alcoolisée que dans l'eau, sauf pour les cellules cultivées en présence d'acides gras insaturés où l'on observe le résultat inverse.La désorganisation des membranes et l'activité autolytique des cellules dépendent à la fois des conditions de culture des bactéries et du milieu dans lequel elles sont mises en suspension.

Les lipides extraits des membranes de bactéries lactiques du vin sont séparés par chromatographie sur couche mince en phospholipides, glycolipides et lipides neutres. Le pourcentage de répartition de chaque classe varie, non seulement en fonction des souches, mais aussi selon leurs conditions de culture.+++Lactic and bacteria of wines are inhibited in fermenting must. Éthanol, fatty acids and other unknow yeast metabolites are responsible for the loss of viability and malolactic activity. Prior results suggest that they induce an alteration of the plasma membrane. Owing to their nature, we assume the lipid constituants to be the target of the inhibitors. So, we have undertaken the study of the membrane lipids of two strains, L. plantarum and L. oenos.After extraction, the samples are analysed by HPTLC. Comparing the strains, the patterns reveal small differences in the distribution of phospholipids, glycolipids and neutral lipids.Some culture factors were investigated for their influence. Within the cell cycle, the distribution of the various classes changes according to the period of incubation. If ethanol is added in the culture medium, neutral lipids decrease by 25 to 50 per cent and glycolipids increase by 30 per cent depending on the age of the culture. Phospholipids remain quite constant.Further researchs are in progress to test the influence of others factors. These results might explain the loss of viability of the bacteria varies when they are added to wine, as well as the variable response to yeast antagonism according to the strains.

Stimulation of malolactic fermentation can be obtained by adding to wine an industrial biomass of L. oenos. Before use, deepfreeze bacteria need to be reactivated according to some special conditions which have been studied. Yeasts concerned in alcoholic fermentation have an influence on malolactic fermentation capacity of wines ; this fact is in connection with some differences observed in wine technology. Among the strains of commercial dry yeasts, the influence of S. cerevisiae is lower than that of S. bayanus.

Une nouvelle méthode pour la détermination de la concentration en C02 des vins est décrite ; elle met en oeuvre une électrode spécifique de mesure des pressions partielles du gaz dissous. Cette technique rapide et précise permet le dosage du C02 dans tous les types de vins. Les résultats des dosages ont été comparés avec ceux donnés par d'autres méthodes classiques qui, sous certaines conditions, donnent des résultats satisfaisants et permettent la généralisation de ce dosage.+++A new method for determining the concentration of C02 of wines is described ; it uses a specific electrode for measuring the partial pressures of dissolved gas. This rapid and precise technique permits the C02 determination in all type of wines. The results have been compared with those given by other classic methods which, in certain conditions, give satisfactory results and permit the generalization of this determination.

Les auteurs présentent une méthode de dosage enzymatique automatisée en flux continu de l'acide malique dans les vins. Afin d'éviter les interférences la formation de NADH est mesurée à 570 nm; la méthode décrite conserve les caractères de spécificité et de sensibilité de la méthode enzymatique manuelle.+++The authors report a continuous flow technic for enzymatic analysis of malic acid in wines. In order to minimize the effect of interfering compounds, the NADH content is read at 570 nm. This method preserve the specificity and sensibility of the enzymatic manual assay.

Les interactions entre levures et bactéries lactiques sont déterminées par la nature des souches en présence, leur population et la constitution chimique du moût et du vin. Normalement, pendant la fermentation, les bactéries lactiques sont inhibées par les produits du métabolisme levurien. Mais dans certaines conditions, la croissance précoce des bactéries provoque une chute de la viabilité des levures et, par conséquent, un ralentissement ou un arrêt de la dégradation des sucres. Tous les mécanismes mis en jeu ne sont pas connus.+++ln wine-making, lactic acid bacteria succeed to yeasts to promote the malolactic fermentation (MLF), after the completion of the alcoholic fermentation. Yeasts are better adapted than bacteria to growth in grape must. So their development easily starts and the alcoholic fermentation triggers soon after the harvest. In the same time, the natural bacterial inoculum decreases, due to an antagonism between these two microorganisms. ln addition to ethanol, fatty acids synthesized by actively growing yeasts exert their toxic effect against lactic acid bacteria. At the end of the alcoholic fermentation, the remaining bacterial population (104 to 103 cell.p.ml) begins growing. It is mainly constitued by Leuconostoc oenos more resistant than lactobacilli. At that time, autolysis products from decline phase yeasts act as bacterial growth factors. Then, when the bacterial population is large enough (about 106 cell.p.ml) MLF happens. So, normally, MLF follows alcoholic fermentation within a few days. But in some conditions, the interactions between yeasts and bacteria do not work in this way. If the weather is particularly hot and dry during the last weeks of the maturation, the pH of the must may be high and generally sulfiting is lowered as there are no rotten grapes. Growing conditions are better than usually for bacteria that, in such a case, compete with yeasts. The bacterial population reach a sufficient level that can actually increase the yeast decline rate. Hydrolase activities of bacteria against yeast cell walls may occur. That leads to a fermentation stuck. These antagonism effects between yeasts and lactic acid bacteria in fermenting must control the wine-making process. Their extent vary with must composition even with both yeast and bacteria strains. Further research is needed to clear up involved machanisms.

La réactivation préalable des bactéries lactiques est indispensable avant l'inoculation des vins. Le mode opératoire est précisé : le milieu optimum est à base de jus de raisin.Différentes préparations industrielles ont été testées au laboratoire. Celles de Leuconostoc œnos ont donné de bons résultats. L'une d'entre elles a été utilisée dans la pratique au cours des deux dernières campagnes de vinification. Les succès obtenus, surtout en 1984 dans des cas particulièrement difficiles montrent bien l'efficacité de ce procédé pour le déclenchement de la fermentation malolactique.+++The previous reactivation of lactic acid bacteria is essential before the inoculation of the wine. The method is specified: the optimium media is made with grape must.Several industrial preparations of bacteria were tried; those constituted with Leuconostoc oenos gave good results. One of them was utilized in practice during the two last vinification campaigns. The success obtained, especially in 1984 in particular difficult cases give proof of the efficiency of this process to start the malolactic fermentation.

Après avoir mis au point un dosage du diacétyle, par chromatographie en phase gazeuse, précis et fiable, la synthèse par Leuconostoc oenos des substances acétoïniques est analysée.L'influence des conditions physico-chimiques du milieu (pH et température) sur cette synthèse est mise en évidence chez Leuconostoc oenos ainsi que la réduction du diacétyle et de l'acétoïne en butanediol-2,3.

La bioluminescence a été appliquée au dénombrement des microorganismes du vin. Il existe une excellente corrélation avec la numération par comptage des colonies sur boîtes de Petri. La simplicité de la manipulation et la rapidité d'obtention des résultats sont les principaux atouts de cette méthode. Toutefois, des recherches sont encore nécessaires, d'une part, pour différencier les levures et les bactéries et, d'autre part, pour abaisser le seuil de détection.+++Bioluminescence was applied to enumerate the microorganisms present in wine. An excellent correlation is obtained by counting colonies grown in Petri dishes. The simplicity of the manipulations and the rapid obtention of results are the principal benefits of this method. Research is still necessary both in the differentiation of yeasts and bacteria and the reduction of the threshold of detection.

A method is described, by wich the malolactic fermentation is induced through direct inoculation with an industrial preparation of L. plantarum (CHL2). When inoculated into must, this homofermentative lactobacillus metabolizes very little sugar, and is unable to produce acetic acid. The inoculated population of bacteria has a high malolactic activity even at low pH values, which is closely related to cell viability. The decarboxylation of malic acid starts immediately after inoculation and proceeds at a high rate during the first days of alcoholic fermentation. As the alcohol concentration rises, the lactobacilli are gradually eliminated, so inoculation with the malolactic culture has to be done very early in the vinification process, in order to achieve a complete malolactic fermentation. At the end of alcoholic fermentation, the malolactic fermentation is finished, and the bacterial inoculum has been completely killed of.The efficiency of this new process is demonstrated in laboratory experiments and field trials with different types of must and different vinification procedures. The advantages of the method, which the winemakers would particularly appreciate, include the direct inoculation mode and considerable gain in terms of production time.

Certaines bactéries lactiques du vin libèrent des polysaccharides qui induisent une importante élévation de viscosité. Elles sont responsables d'une maladie appelée maladie de la «graisse» ou des vins «filants» décrite pour la première fois par PASTEUR (1866). Au début du siècle, GAYON (1900) puis LABORDE (1904) se sont intéressés à l'isolement de ces bactéries et à la nature des colloïdes produits.En 1988, LONVAUD-FUNEL et JOYEUX ont isolé et identifié quelques souches de bactéries lactiques du genre Pediococcus et reproduit la maladie sur milieu modèle. Nous rapportons ici la purification et la structure moléculaire du polysaccharide produit par ces souches ainsi que les conditions de culture favorisant sa biosynthèse (LLAUBERÈS, 1988).