Relationship Between Phospholipid and Sterol Contents inSaccharomyces cerevisiaeandTorulaspora delbrueckiiand their Fermentation Activity in Grape Musts

The yeast growth, viability rate of resting yeast cells, and the fermentation activity of Saccharomyces cerevisiae and Torulaspora delbrueckii in grape musts with high sugar contents can be increased by aeration. In S. cerevisiae, such an increase is related to the cell contents in sterols and phospholipids, while in T. delbrueckii it is also dependent on oxygen, the presence of which is essential to the normal development of the yeast growth and the fermentation process. The more marked dependency of the biosynthesis of sterols and phospholipids on oxygen in T. delbrueckii and its great relevance to cell growth may be the origin of the early disappearance of this species from grape musts during spontaneous fermentations.