Isolated yeast populations of Chardonnay grape must during spontaneous fermentation were compared to those isolated on grape berries and in a winery environment before the arrival of the harvest (air, floor, winery equipment) and in the... more
Isolated yeast populations of Chardonnay grape must during spontaneous fermentation were compared to those isolated on grape berries and in a winery environment before the arrival of the harvest (air, floor, winery equipment) and in the air through time. Two genera of yeast, Hanseniaspora and Saccharomyces, were isolated in grape must and in the winery environment before the arrival of the harvest but not on grape berries. The genus Hanseniaspora represented 27% of isolates in the must and 35% of isolates in the winery environment. The isolates of these two species were discriminated at the strain level by Fourier transform infrared spectroscopy. The diversity of these strains observed in the winery environment (26 strains) and in must (12 strains) was considerable. 58% of the yeasts of the genus Hanseniaspora isolated in the must corresponded to strains present in the winery before the arrival of the harvest. Although the proportion and number of strains of the genus Hanseniaspora decreased during fermentation, some strains, all from the winery environment, subsisted up to 5% ethanol content. This is the first time that the implantation in grape must of populations present in the winery environment has been demonstrated for a non-Saccharomyces genus.
The efficiency of the FT-IR technique for studying the inter- and intra biodiversity of cultivable non-Saccharomyces yeasts (NS) present indifferentmust sampleswas examined. Infirst, the capacity of the technique FT-IRto study the global... more
The efficiency of the FT-IR technique for studying the inter- and intra biodiversity of cultivable non-Saccharomyces yeasts (NS) present indifferentmust sampleswas examined. Infirst, the capacity of the technique FT-IRto study the global diversity of a given sample was compared to the pyrosequencing method, used as a reference technique. Seven different genera (Aureobasidium, Candida, Cryptococcus, Hanseniaspora, Issatchenkia, Metschnikowia and Pichia)wereidentified by FT-IR and also by pyrosequencing. Thirty-eight other genera were identified by pyrose- quencing, but together they represented less than 6% of the average total population of 6 musts. Among the species identified, some of thempresentorganoleptic potentials inwinemaking,particularly Starmerella bacillaris (synonym Candida zemplinina). So in a second time, we evaluated the capacity of the FT-IR technique to discriminate the isolates of this species because few techniques were able to study intraspecific NS yeast biodiversity. The results obtained were validated by using a classic method as ITS sequencing. Biodiversity at strain level was high: 19 different strains were identified from 58 isolates. So, FT-IR spectroscopy seems to be an accurate and reliable method for identifying major genera present in themusts. The two biggest advantages of the FT-IR are the capacity to characterize intraspecific biodiversity of non-Saccharomyces yeasts and the possibility to discriminate a lot of strains.
Different genera and/or species of yeasts present on grape berries, in musts and wines are widely described. Nevertheless, the community of non-Saccharomyces yeasts present in the cellar is still given little attention. Thus it is not... more
Different genera and/or species of yeasts present on grape berries, in musts and wines are widely described. Nevertheless, the community of non-Saccharomyces yeasts present in the cellar is still given little attention. Thus it is not known if the cellar is a real ecological niche for these yeasts or if it is merely a transient habitat for populations brought in by grape berries during the winemaking period. This study focused on three species of non-Saccharomyces yeasts commonly encountered during vinification: Starmerella bacillaris (synonymy with Candida zemplinina), Hanseniaspora guilliermondii and Hanseniaspora uvarum. More than 1200 isolates were identified at the strain level by FT-IR spectroscopy (207 different FTIR strain pattern). Only a small proportion of non-Saccharomyces yeasts present in musts came directly from grape berries for the three species studied. Some strains were found in the must in two consecutive years and some of them were also found in the cellar environment before the arrival of the harvest of second vintage. This study demonstrates for the first time the persistence of non-Saccharomyces yeast strains from year to year in the cellar. Sulfur dioxide can affect yeast populations in the must and therefore their persistence in the cellar environment.
Although 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... more
Although 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, H. uvarum, Metschnikowia sp., Pichia membranifaciens, Saccharomyces cerevisiae and Starmerella bacillaris) was evaluated. The species A. pullulans and St. bacillaris appeared to be more resistant to copper than the other species tested. The species A. pullulans, H. guilliermondii and Metschnikowia sp. had the highest sulfur resistance. Thus, only isolates of the species A. 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 A. pullulans for viney...
Diet quality is critical for animal development and survival. Fungi can provide nutrients that are essential to organisms that are unable to synthetize them, such as ergosterol in Drosophila melanogaster. Drosophila studies examining the... more
Diet quality is critical for animal development and survival. Fungi can provide nutrients that are essential to organisms that are unable to synthetize them, such as ergosterol in Drosophila melanogaster. Drosophila studies examining the influence of yeast quality in the diet have generally either provided the diet over the whole life span (larva to adult) or during the adult stage and have rarely focussed on the juvenile diet. Here, we tested the effect of yeast quality in the larval diet on pre-adult development and adult weight, survival, reproduction and food preference. The yeast Saccharomyces cerevisiae was added in three forms in three treatments-live, heated or dried-to food used as the juvenile diet or was not added (empty treatment). Adults resulting from the larvae raised on these four juvenile diets were all maintained on a similar standard laboratory food diet. Our data indicate that yeast quality in the juvenile diet affects larva-to-pupa-but not pupa-to-adult-developm...
Les effets de differentes activites anthropiques (vignoble, cuverie) sur les populations fongiques du raisin au vin ont ete etudies. Afin de caracteriser ces effets, il etait necessaire d’avoir acces a la diversite globale des populations... more
Les effets de differentes activites anthropiques (vignoble, cuverie) sur les populations fongiques du raisin au vin ont ete etudies. Afin de caracteriser ces effets, il etait necessaire d’avoir acces a la diversite globale des populations (pyrosequencage et IR-TF) mais egalement a la diversite intraspecifique (IR-TF). La spectroscopie a ainsi ete validee pour sa capacite a caracteriser la population globale et a discriminer les souches pour trois especes de levures non-Saccharomyces (NS). Pour la premiere fois, il est demontre que la baie de raisin constitue une source limitee pour les levures NS alors que la cuverie semble constituer une source importante; l’air etant un vecteur important de dissemination de ces levures. De plus, la persistance et la reimplantation des levures NS dans le mout l’annee suivante ont ete demontrees. Les activites anthropiques etudiees modifient la diversite fongique. Une biodiversite plus faible pour les raisins de la modalite biologique a ete mesuree ...
Although the functions and structural roles of sterols have been the subject of numerous studies, the reasons for the diversity of sterols in the different eukaryotic kingdoms remain unclear. It is thought that the specificity of sterols... more
Although the functions and structural roles of sterols have been the subject of numerous studies, the reasons for the diversity of sterols in the different eukaryotic kingdoms remain unclear. It is thought that the specificity of sterols is linked to unidentified supplementary functions that could enable organisms to be better adapted to their environment. Ergosterol is accumulated by late branching fungi that encounter oxidative perturbations in their interfacial habitats. Here, we investigated the antioxidant properties of ergosterol using in vivo, in vitro, and in silico approaches. The results showed that ergosterol is involved in yeast resistance to tert-butyl hydroperoxide and protects lipids against oxidation in liposomes. A computational study based on quantum chemistry revealed that this protection could be related to its antioxidant properties operating through an electron transfer followed by a proton transfer mechanism. This study demonstrates the antioxidant role of erg...
