Zeolite NaY at 5 g dm(-3) concentration, was selected to improve the production of ethanol fermentation by Saccharomyces bayanus from high glucose concentration media. The highest ethanol productivity (3.07 g dm(-3) h(-1)) was obtained from a 220 g dm(-3) initial glucose concentration, while the highest ethanol concentration (130 g dm(-3)) was obtained from a 350 g dm(-3) glucose medium. The zeolite is believed to have acted as a pH regulator, maintaining the pH value around 3.7-3.8. Under these conditions cellular viability was preserved and metabolic activity was maintained. Thus all the glucose was consumed, and high ethanol productivity and concentration were obtained. Therefore, the addition of zeolite improved ethanol production from high concentrations of glucose by Saccharomyces bayanus.