Ethanol fermentation of very high gravity (VHG) maize mashes by Saccharomyces cerevisiae with spent brewer's yeast supplementation

•Ethanol fermentation of VHG maize mashes with spent brewer's yeast supplementation was conducted.•Supplementation led to decrease in ethanol production rate.•Mashes supplementation shorten the fermentation time.•Spent yeast supplementation increases ethanol yield.

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 dm−3 in supplemented mashes (120.74 g dm−3 in the control sample) which corresponded with practical ethanol yields of 78.05–91.85% (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.