The influence of ethylenediaminetetra acetic acid (EDTA), potassium ferrocyanide and zeolite X on ethanol production from sugar beet molasses by Saccharomyces cerevisiae was studied. For all of the three substances used, the effect was more pronounced when added to the fermentation medium rather than to the growth medium; 1.9 mmol dm(-3) potassium ferrocyanide caused an increase in the final ethanol concentration of about 16.4% and 47.5% with respect to control culture on addition to growth and fermentation media respectively. The greatest stimulation in product yield was obtained with zeolite X introduced during the fermentation stage; 8.0 g dm(-3) zeolite X increased ethanol concentration by 53.3%.