Genetic and Chromosomal Stability of Wine Yeasts

The conversion of grape juice into wine is a complex fermentation process in which yeasts play a central role. The composition of the yeast flora in the fermenting must vary according to geographic location, climatic conditions, and grape variety (e.g., ref. 1 ). During the early phase of fermentation, apiculate yeasts belonging to the species Kloeckera apiculata (Hanseniaspora uvarum) are dominant, but Candida, Pichia, Rhodotorula, Kluyveromyces, Hansenula, Metschnikowia , and Saccharomyces strains can also be detected (1 ). Most of them die off when the ethanol concentration rises to around 4% (2 ) and leave Saccharomyces to complete the fermentation. The major Saccharomyces species found among wine yeasts is S. cerevisiae , but S. bayanus can also be detected. The S. cerevisiae flora itself is also variable, it can change in the course of fermentation and various strains can grow simultaneously as subpopulations (e.g., ref. 3 –6 ).