Saccharomyces bayanus var. uvarum plays an important role in the fermentation of red wine from the D.O. Ribera del Duero. This is due to the special organoleptic taste that this yeast gives the wines and their ability to ferment at low temperature. To determine the molecular factors involved in the fermentation process at low temperature, a differential proteomic approach was performed by using 2D-DIGE, comparing, qualitatively and quantitatively, the profiles obtained at 13 and 25°C. A total of 152 protein spots were identified. We detected proteins upregulated at 13°C that were shown to be related to temperature stress, the production of aromatic compounds involved in the metabolism of amino acids, and the production of fusel alcohols and their derivatives, each of which is directly related to the quality of the wines. To check the temperature effects, an aromatic analysis by GC-MS was performed. The proteomic and "aromatomic" results are discussed in relation to the oenological properties of S. bayanus var. uvarum.

Molecular characterization of wine yeast population during spontaneous fermentation in biodynamic wines from Ribera del Duero D.O. located at northern plateau of Spain has been carried out during two consecutive years. A total of 829 yeast strains were isolated from the samples and characterized by electrophoretic karyotype. The results show the presence of three population of yeast differentiated by their electrophoretic karyotypes, (1) non-Saccharomyces yeast dominant in the initial phase of the fermentations (NS); (2) Saccharomyces bayanus var uvarum detected mainly mid-way through the fermentation process at 20-25 °C; and (3) Saccharomyces cerevisiae which remained dominant until the end of the fermentation. This is the first study showing the population dynamic of S. bayanus var. uvarum in red wines produced in Ribera del Duero that could represent an important source of autochthonous wine yeasts with novel oenological properties.

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