In sterile grape juice medium a strain of Saccharomyces cerevisiae var. ellipsoideus, under proliferating conditions, converted a small portion of added α-amino- n-butyric acid to n-propanol. The yield was 2.8% on the basis of utilization of one isomer of the synthetic α-amino- n-butyric acid added, or 0.16% on the basis of the ethanol produced. Without added amino acid, no detectable n-propanol was formed. In sterile glucosephosphate buffer solution containing added amino acid, the metabolic activity of heavy inoculations of the same yeast did not produce a detectable amount of n-propanol.