Improvement of very high gravity ethanol fermentation by media supplementation using Saccharomyces cerevisiae

The final ethanol concentration achieved was increased by 17% (to 103 g eth anol/l) when excess assimilable nitrogen was added to the batch very high g ravity (VHG) ethanolic fermentations by Saccharomyces cerevisiae. The suppl ementation of the media with 12 g yeast extract l(-1), 0.3 g cell walls l(- 1), 3 g glycine l(-1) and 20 g soya flour l(-1) led to halving reduction of the fermentation time to 28 h. The ethanol productivity was enhanced by mo re than 50% (to achieved value 3.3 g l(-1) h(-1)).