Combined use of three methods for high concentration ethanol production by Saccharomyces cerevisiae

Summary Ethanol concentration and fermentation productivity using Saccharomyces cerevisiae were substantially increased in shake flask cultures with a normal inoculum by combining 3 methods: (a) by making nutrient additions to the standard medium for ethanol production, (b) by immobilizing the cells in alginate beads and (c) by using a glucose step-feeding batch process. Ethanol concentration by free yeast was improved from 5.9% (w/w) to 9.6% (w/w) when a further 0.8% yeast extract and 1% animal peptone were added to the standard 30% (w/v) glucose nutrient medium. This was further increased to 12.8% (w/w) by using alginate immobilized yeast. The ethanol concentration was increased again, to 15.0% (w/w) by using the glucose step-feeding batch process.