CONICET | Buscador de Institutos y Recursos Humanos

S. cerevisiae is the predominant species responsible of the alcoholic fermentation; however other closely related species, belonging to the new Saccharomyces genus may have an important role Turing the fermentation processes. Alcohol fermentation are not the best suited medium for the development of Saccharomyces yeast. Along their evolution, yeasts have suffered diverse selective processes to become adapted to the fermentation conditions. These events led to the unconscious domestication of the industrial yeasts possessing especial physiological and genetic properties. In the case of the Saccharomyces yeasts, one of the most interesting mechanisms, involved in their adaptation to industrial processes, is the generation of interspecific hybrids. Saccharomcyes hybrid strains have been isolated form different fermentation processes. We described, for the fist time, the presence of natural wine hybrids among S. cerevisiae and S. kudriavzevii. The oenological characterization of wine hybrids showed that these strains acquired the ethanol tolerance and the ability to growth in media containing high level of sugar from the S. cerevisiae parent and improved growth at lower temperatures from the S. kudriavzevii parent. the DNA chip analyses of yeast gene expression during microvinification, indicate that hybrids exhibit a significant higher expression of the genes involved in the glycerol synthesis (GPP1 and 2); in the adaptation (stress response) to low temperatures due to an over-expression of the genes related with the synthesis of ergosterol (ERG1 and ERG3, ERG11, ERG26) and of cold-shock genes (TIR1, TIR2, PAU3, PDR5, YHB1 and TIP1). In addition, we also detected and over-expression of some genes encoding aminoacid transporters (AGP1, FUR4, RHB1, BAP3). As we describe previously the species of the genus Saccharomyces are the main yeast responsible for alcoholic fermentation of grape juice during winemaking. This makes wine strains of this species perfect target for the improvement of wine technology and quality. Although variant selection probably is the most used techniques, others traditional techniques based on classical genetic like mutagenesis, hybridization (mating, spore-cell mating). rare mating, cytoduction and spheroplast fusion have been used followed by selection for broad trains, such as fermentation capacity, ethanol tolerance and absence of off-flavours (e.g. hydrogen sulphide). These methods are especially advantageous to improve to improve and combine traits under polygenic control and do not give rise to products that are included in the definition of genetically organisms (OGM). the relevance of the different techniques applied to improves wine yeasts including the genetically modified organisms and their potential application, and factors affecting their commercial viability will be discussed in this review.

enviar mensaje