Las levaduras como bancos de prueba en las Ciencias de la Vida

Trabajo presentado en el Simposio Internacional 2Las levaduras como bancos de prueba en las Ciencias de la Vida", celebrado en Madrid el 17 y 18 de octubre de 2016.Saccharomyces cerevisiae is the main yeast species involved in traditional or industrial fermentation of sugar rich substrates, including the production of fermented foods and bioethanol. However, other yeast, as well as bacteria, play a relevant role in these fermentation processes, especially fermented foods prepared with non-sterilized raw materials. For example, Hanseniaspora/Kloeckera, Pichia, Candida or Metschnikowia strains predominate during the initial stages of spontaneous grape wine fermentation. Some decades ago oenologists learned to master wine fermentation processes by using S. cerevisiae starter yeasts. Despite the gain in reliability of the fermentation process and overall quality of wines, the rather quick replacement of natural microbiota during the first stages of grape juice fermentation have leaded to a relative uniformity of the sensorial profile of commercial wines. Evidence has also been accumulated during the last twenty years on the positive contribution to wine quality of some of these indigenous yeast species during spontaneous fermentation. In this context, one of the late trends in wine microbiology is gathering together the advantages of microbiological control and those of the metabolic diversity of natural fermentation, by developing yeast starters from wine yeast species alternative to S. cerevisiae. In addition to their contribution to the aromatic profile, the metabolic features of some of these yeasts can eventually be managed to reduce alcohol content of wines through aerobic respiration. Industrial use of non-conventional yeasts and/or non-conventional fermentation conditions, including aerated fermentation (to allow for partial respiration of sugars) and multispecies starters (either in sequential or simultaneous inoculation), opens new questions whose answers will be interesting both from an academic or an applied perspective. This talk will deal with some of these topics, including the impact of oxygenation on the metabolism of some yeast species, beyond the direct impact on respiration; the relationship between fermentation under micro-oxygenated conditions and acetic acid production; or the early responses of yeast strains to the presence of potential competitors in the same culture medium.Peer Reviewe