Differences in the course of enzymatic degradation of maize starch during alcoholic fermentation run according to the technology of pressureless liberation of starch (PSL) have been presented. Two variants of fermentation have been compared: (i) with the application of a full dose of an amyloglucosidase preparation and Saccharomyces cerevisiae As-4 yeasts and (ii) a dose of amyloglucosidase reduced by 25% and 1-7-43 strain (fusant between S. cerevisiae and Saccharomyces diastaticus) characterized by amylolytic properties. The effects of different concentrations of saccharides accessible for yeasts on the parameters of fermentation and composition of by-products have been studied. Differences in concentrations of product fractions accessible for yeasts caused by the reduced by 25% dose of SAN Super 240 L preparation did not result in deterioration of the final biotechnological factors of fermentation conducted with the application of 1-7-43 yeasts in comparison with As-4. It was found that the concentration of aldehydes was higher by about 10% in distillates obtained from mashes fermented with 1-7-43 yeasts. Moreover, the concentration of higher alcohols in the above-mentioned distillates was lower by 15% in comparison with that obtained by using As-4 yeasts. It was caused by a lower percentage of isobutanol and amyl alcohols. (c) 2005 Elsevier Ltd. All rights reserved.