Editorial: Non-conventional Yeast in the Wine Industry

The alcoholic fermentation of grape musts to wines is a rather complex process that involves the sequential development of microorganisms, mainly yeasts, but also filamentous fungi, lactic acid bacteria, etc. In the early stages of wine fermentation, several yeast species may be present but, as the alcohol concentration increases, Saccharomyces species progressively take over. The winemaking process cannot be understood without knowing how the different microorganisms leave their microbial footprint. The footprint depends on how long these microorganisms are present and their dominance during the winemaking process. The first source of this microbial population diversity is grape, which is an ecological niche for freely proliferating microorganisms. The grapes have populations of native or indigenous yeasts that are between 10 4 and 10 6 cells/g of grapes, which are mainly Non-Saccharomyces yeasts. The populations of Saccharomyces are very low in grapes, although they are not completely absent. The Non-Saccharomyces strains have been regarded for many years as the responsible for wine spoilage and different preventive actions have been taken to avoid them. These populations change slightly when they enter in contact with the cellar environment (presses, pumps, tanks) where they join the resident microbiota. This microbiota is rare in new wineries, particularly if the equipment has not been used previously. The cellar is a good niche for S. cerevisiae, which becomes the main cellar-resident yeast (Beltran et al., 2002). According with the distribution of yeasts in the grape surface, yeasts with low fermentation activity, such as Candida spp. spp. and Schizosaccharomyces spp. are predominant in grape musts and during the early stages of fermentation. Saccharomyces cerevisiae develops shortly afterwards, to become the dominating microorganism and completing the wine fermentation. S. cerevisiae strains have unique physiological properties that are not found in other yeasts. The most important is the high ability to ferment sugars vigorously to produce alcohol under both aerobic and anaerobic conditions. This aptitude allows them to colonize quickly substrates with high sugar concentrations and overgrow other yeasts (Fleet and Heard, 1993). The role of S. cerevisiae yeasts is not only related with conducting the alcoholic fermentation, but is also heavily related to wine quality. The activities of the different yeast species and strains have an impact on the sensory profiles of wine by increasing its complexity and organoleptic richness (Fleet, 2003). Currently, winemakers use available commercial starters of S. cerevisiae to have a reproducible and predictable wine by controlling …