Differences Between Indigenous Yeast Populations in Spontaneously Fermenting Musts From V. vinifera L. and V. labrusca L. Grapes Harvested in the Same Geographic Location.

Yeast communities associated with Vitis vinifera L. ecosystems have been widely characterized. Less is known, however, about yeast communities present in grapes and fermenting musts from Vitis non-vinifera ecosystems. Moreover, there are no comparative studies concerning yeast communities in grapes from V. vinifera L. and non-vinifera Vitis species in vineyards from a shared terroir. In this work, we have used a culture-dependent strategy, phenotypic analyses, and molecular genotyping, to study the most representative yeast species present in spontaneously fermenting musts of grapes harvested from neighboring V. vinifera L. (cv. Malbec) and V. labrusca L. (cv. Isabella) vineyards. Phenotypic analyses of H2S production, ethanol tolerance and carbon utilization, on randomly selected strains of each Hanseniaspora uvarum, Starmerella bacillaris and Saccharomyces cerevisiae strains, as well as microsatellite genotyping of S. cerevisiae isolates from each the Malbec and Isabella grape musts, suggest that V. vinifera L. and V. labrusca L. ecosystems could harbor different yeast strain populations. Thus, microbial communities in exotic Vitis species may offer opportunities to look for unique yeast strains that could not be present in conventional V. vinifera L. ecosystems.

Isolation and Identification of the Indigenous Yeast Population during Spontaneous Fermentation of Isabella (Vitis labrusca L.) Grape Must.

Grape must harbors a complex community of yeast species responsible for spontaneous alcoholic fermentation. Although there are detailed studies on the microbiota of Vitis vinifera L. grapes, less is known about the diversity and behavior of yeast communities present on fermenting grape must from other species of Vitis. In this work, we used a culture-dependent method to study the identity and dynamics of the indigenous yeast population present during the spontaneous fermentation of Isabella (Vitis labrusca L.) grape must. Alcoholic fermentation was conducted using standard enological practices, and the associated non-Saccharomyces and S. cerevisiae yeast community was analyzed using selective growth media and 5.8-ITS DNA sequencing. Candida californica, Candida hellenica, Starmerella bacillaris (synonym Candida zemplinina), Hanseniaspora uvarum, and Hanseniaspora vineae were the main non-Saccharomyces species identified on Isabella fermenting must. Issatchenkia hanoiensis, a yeast species rarely found on Vitis vinifera L. grapes, was also recognized on Isabella grape must. Candida azymoides, Candida californica and Pichia cecembensis, identified in this work on Isabella fermenting must, have not previously been found on Vitis vinifera L. grape must. Interestingly, C. azymoides, I. hanoiensis and P. cecembensis have recently been isolated from the surface of Vitis labrusca L. grapes from vineyards in the Azores archipelago, suggesting that specific Vitis-yeast species associations are formed independently of geographic origin. We suggest that C. azymoides, C. californica, and P. cecembensis are yeast species preferentially associated with Vitis labrusca L. grapes. Specific biological interactions between grapevines and yeast species may underlie the assembly of differential Vitis-microbial communities.