INVESTIGADORES
LOPES christian ariel
congresos y reuniones científicas
Título:
Fermentative stress adaptation of hybrids within the species of the genus Saccharomyces
Autor/es:
QUEROL A.; COMBINA M.; LOPES C.A.; BELLOCH C.; PÉREZ-TORRADO R.; PÉREZ L.; BARRIO E.
Lugar:
Mar del Plata, Argentina
Reunión:
Congreso; VI Congreso Latinoamericano de Micología; 2008
Institución organizadora:
Asociación Latinoamericana de Micología
Resumen:
S. cerevisiae is the predominant species responsible of the alcohol fermentation;however other closely related specie, belonging to the new Saccharomyces genus mayhave an important role during fermentation processes. Alcohol fermentations are not thebest suited medium for the development of Saccharomyces yeasts. Along theirevolution, yeasts have suffered diverse selective processes to become adapted to thefermentation conditions. These events led to the unconscious "domestication" of the"industrial" yeasts possessing special physiological and genetic properties. In the case ofSaccharomyces yeasts, one of the most interesting mechanisms, involved in theiradaptation to industrial processes, is the generation of interespecific hybrids.Saccharomyces hybrids strains have been isolated from different fermentationprocesses. We described, for the first time, the presence of natural wine hybrids amongS. cerevisiae and S. kudriavzevii. The oenological characterization of wine hybridsshowed that these strains acquired the ethanol tolerance and the ability to grow in mediacontaining high levels of sugar from the S. cerevisiae parent and improved growth atlower temperatures from the S. kudriavzevii parent. The DNA chip analyses of yeastgene expression during microvinification, indicate that hybrids exhibit a significanthigher expression of the genes involved in the glycerol synthesis (GPP1 and 2); in theadaptation (stress response) to low temperatures due to an over-expression of the genesrelated with the synthesis of ergosterol (ERG1 and ERG3, ERG11, ERG26) and of coldshockgenes (TIR1, TIR2, PAU3, PDR5, YHB1 and TIP1). In addition, we also detectedan over-expression of some genes encoding amino acid transporters (AGP1, FUR4,RHB1, BAP3). As we described previously the species of the genus Saccharomyces arethe main yeast responsible for alcoholic fermentation of grape juice during winemaking. This makes wine strains of this species perfect target for the improvement ofwine technology and quality. Although variant selection probably is the most usedtechniques, other traditional techniques based on classical genetic like mutagenesis,hybridization (mating, spore-cell mating), rare mating, cytoduction and spheroplastfusion have been used followed by selection for broad traits, such as fermentationcapacity, ethanol tolerance and absence of off-flavours (e.g. hydrogen sulphide). Thesemethods are specially advantageous to improve and combine traits under polygeniccontrol and do not give rise to products that are included in the definition of geneticallymodified organisms (GMOs). The relevance of the different techniques applied toimproves wine yeasts including the genetically modified organisms and their potentialapplication, and factors affecting their commercial viability will be discussed in thisreview. Acknowledgements: This work was supported by CICYT grant (AGL2006-12703-CO2) from the Spanish Ministerio de Ciencia y Tecnología to A.Q. and E.B.