The aim of the work was to study how fermentations with only one nitrogen source (ammonia) and fermentations with a combined nitrogen source (ammonia and amino acids, as in grape must) can affect the membrane fatty acid composition of Saccharomyces cerevisiae. Fermentations were carried out at 25°C and pH 3.5 in 500-ml bottles filled with 450 ml of the medium with the different nitrogen sources. A commercial Saccharomyces cerevisiae strain was then inoculated. The fermentation time of the medium with ammonia as the sole nitrogen source was shorter (8 days to consume all fermentable sugars) and the maximal fermentation rate higher compared to the combined source. Even though previous studies showed that amino acids increase the fermentation rate and decrease the fermentation time, in the present work the mixed source did not lead to a better fermentation rate than the ammonia source. The fatty acids content in yeasts at the end of the fermentation was similar in cells grown in ammonia (17.90 mg g-1 dry cell weight) or amino acids (15.42 mg g-1 dry cell weight) media as sole nitrogen source and higher than that of cells fermented in a medium with combined ammonia and amino acids. Cells grown in the mixed nitrogen source showed fatty acids with a higher unsaturation degree than cells grown on sole ammonia. (We advise you to read the entire article. Original title: Effect of the nitrogen source on the fatty acid composition of Saccharomyces cerevisiae)