The subject of this research project was ethanol productivity from very high gravity maize
mashes supplemented with spent brewer’s yeast as a nutrient source. Batch fermentation
of maize mashes (360 g of maize per kilogram of mash) supplemented with 30 g of spent
brewer’s yeast’s wet biomass, dried spent brewer’s yeast and yeast extract per kilogram of
mash was conducted for 96 h at 30 C. In all supplemented mashes higher ethanol production
rate was observed in comparison to the control sample, especially in the initial
stages of fermentation. After 96 h fermentation the ethanol concentration ranged from
120.95 to 142.34 g dm3 in supplemented mashes (120.74 g dm3 in the control sample)
which corresponded with practical ethanol yields of 78.05e91.85% (77.91% in the control
sample). It was also important that maximum ethanol yield in supplemented mashes was
achieved after ca. 48 h and 72 h of fermentation while in the control sample ethanol
production continued until the end of the process.