Influence of some factors on autolysis of Oenococcus oeni

Oenococcus oeni was able to autolyse after transfer to water at 40 degreesC. Cells harvested in the mid-log phase autolyse more rapidly than in other growth phases. Optimum conditions of pH (broad scale,vith two maxima at 4.0 and 7.0) and temperature (40 degreesC) have also been elucidated. Trypsin and EDTA appeared to enhance cell wall autolysis. The activity of several enzymes, namely an amidase or endopeptidase and a N-acetyl-β-D-glucosaminidase, were shown to be involved in the autolytic process, thereby releasing soluble cell wall fragments and nitrogen compounds

Incidence d'une activité glucanasique exogène sur le devenir des macromolécules levuriennes du vin

L'addition d'une preparation enzymatique contenant des activités pectinasiques et β (1→ + 3) glucanasiques sur les lies levuriennes est testée en rnilieu vin et en milieu synthétique. Son intérêt est double: hydrolysedes macromolécules présentes initialement dans le milieu et accéleration de la désorganisation du réseau glucanes de la paroi levurienne. Ceci se traduit par une augmentation de la libération de mannoprotéines d'environ 50 kDa.Influence of exogenous glucanase activity on the yeast macromolecules in wineThe addition of an enzymatic preparation containing pectinase and beta (1 --> 3) glucanase activities on yeast lees was tested in wine and a synthetic medium. We observed the hydrolysis of the macromolecules which were present initially in the medium and an acceleration of hydrolysis of cell wall glucans. The liberation of mannoproteins about 50 kDa was increased

Contribution à l'étude de la dégradation de l'acide L-malique par les bactéries lactiques isolées du vin: Effet stimulant des autolysats de levures

Degradation of L-malic acid by lactic bacteria isolated from wine:Stimulating effect of yeast autolysatesFive yeast autolysates used in the present study showed very different levels of proteolysis. They had a major effect on the growth and the malolactic activity of four strains of lactic acid bacteria isolated from wine (Lactobacillus hilgardii, Leuconostoc mesenteroi'des, Leuconostoc oenos strain 44-40 and Leuconostoc oenos strain B). This effect was always stimulating, but there was considerable interaction between the type of autolysate and the bacterial strain on the one hand and the composition of the culture medium (pH, ethanol) on the other hand

Activités enzymatiques: glycosidases et peptidase chez Leuconostoc oenos au cours de la croissance bactérienne. Influence des macromolécules de levures

Les macromolécules d'origine pariétale (polysaccharides et proteines) libérées après autolyse de Saccharomyces cerevisiae stimulent fortement le développement de L. oenos en milieu synthétique. Ceci se traduit par un raccourcissement de la phase de latence et par une augmentation de la biomasse formée. Différentes activités enzymatiques (α-D et β-D-glucosidases, N-acétyl-β-D-glucosaminidase, peptidase), mesurées sur cellules entières de L. oenos, augmentent significativement dès la phase de latence lorsque les bactéries sont cultivées en présence de ces macromolécules de levures. Les déterminations du pH optimum et de la température optimale des trois osidases, pariétales pour l'α-D-glucosidase et la β-D-glucosidase et endocellulaire ou périplasmique pour la N-acétyl-β-D-glucosaminidase, montrent que L. oenos possède un équipement enzymatique fonctionnel au pH du vin et aux températures de conservation du vin capable d'hydrolyser partiellement les macromolécules de levures, naturellement présentes en fin de fermentation alcoolique dans le milieu.Osidasic and peptidasic activities in Leuconostoc oenos during bacterial growth. Influence of macromolecules of yeastsCell-wall polyosides and proteins liberated by Saccharomyces cerevisiae after autolysis stimulated the growth of Leuconostoc oenos in a synthetic environment by a shortening of the latence period and a marked increase of bacterial biomass. Activities of alpha-D and beta-D-glucosidases, N-acetyl-beta-D-glucosaminidase and peptidase, in whole cells of L. oenos, increased from the latence period on lactic acid bacteria cultivated with these macromolecules. Temperature optima and pH optima of cell-wall bound alpha- and beta-glucosidases and of soluble N-acetyl-beta-glucosaminidase, indicated that L. oenos is able to hydrolise partially the yeast's macromolecules present in the wine at the end of alcoholic fermentation

A mathematical model of the link between growth and L-malic acid consumption for five strains of Oenococcus oeni

In winemaking, after the alcoholic fermentation of red wines and some white wines, L-malic acid must be converted into L-lactic acid to reduce the acidity. This malolactic fermentation (MLF) is usually carried out by the lactic acid bacteria Oenococcus oeni. Depending on the level of process control, selected O. oeni is inoculated or the natural microbiota of the cellar is used. This study considers the link between growth and MLF for five strains of O. oeni species. The kinetics of growth and L-malic acid consumption were followed in modified MRS medium (20 °C, pH 3.5, and 10 % ethanol) in anaerobic conditions. A large variability was found among the strains for both their growth and their consumption of L-malic acid. There was no direct link between biomass productivities and consumption of L-malic acid among strains but there was a link of proportionality between the specific growth of a strain and its specific consumption of L-malic acid. Experiments with and without malic acid clearly demonstrated that malic acid consumption improved the growth of strains. This link was quantified by a mathematical model comparing the intrinsic malic acid consumption capacity of the strains

The sensitivity of yeasts and yeasts-like fungi to copper and sulfur could explain lower yeast biodiversity in organic vineyards

International audienceAlthough differences in yeast biodiversity have often been found between vineyards subjected to organic protection or conventional protection, little is known about the effect of copper and sulfur fungicides (the only fungicides allowed in organic farming) on yeast populations. The sensitivity to copper and sulfur of 158 yeast isolates of seven different species (Aureobasidium pullulans, Hanseniaspora guilliermondii, Hanseniaspora uvarum, Metschnikowia sp., Pichia membranifaciens, Saccharomyces cerevisiae and Starmerella bacillaris) was evaluated. The species Aureobasidium pullulans and Starmerella bacillaris appeared to be more resistant to copper than the other species tested. The species Aureobasidium pullulans, Hanseniaspora guilliermondii and Metschnikowia sp. had the highest sulfur resistance. Thus, only isolates of the species Aureobasidium pullulans exhibited high resistance to both antifungal agents. These results may explain the lower diversity of yeasts present on berries and the strong dominance of the species Aureobasidium pullulans for vineyards protected by copper or sulfur-based fungicides compared to other vineyards reported by several studies

Wine microbiome : A dynamic world of microbial interactions

International audienceMost fermented products are generated by a mixture of microbes. These microbial consortia perform various biological activities responsible for the nutritional, hygienic, and aromatic qualities of the product. Wine is no exception. Substantial yeast and bacterial biodiversity is observed on grapes, and in both must and wine. The diverse microorganisms present interact throughout the winemaking process. The interactions modulate the hygienic and sensorial properties of the wine. Many studies have been conducted to elucidate the nature of these interactions, with the aim of establishing better control of the two fermentations occurring during wine processing. However, wine is a very complex medium making such studies difficult. In this review, we present the current state of research on microbial interactions in wines. We consider the different kinds of interactions between different microorganisms together with the consequences of these interactions. We underline the major challenges to obtaining a better understanding of how microbes interact. Finally, strategies and methodologies that may help unravel microbe interactions in wine are suggested