The aim of this investigation was to attain high ethanol concentration by concentrating sweet sorghum juice using a two-step membrane separation process. Ultrafiltration permeation of the juice was used to remove residues, followed by nanofiltration concentration to increase the sugar concentration. The concentrated juice containing 180.0gL<SUP>-1</SUP> sucrose, 59.3gL<SUP>-1</SUP> glucose and 49.3gL<SUP>-1</SUP> fructose supplemented with nitrogen sources (10 and 20gL<SUP>-1</SUP> of yeast extract and polypeptone, respectively) was fermented by Saccharomyces cerevisiae BY4741 to produce 133.5gL<SUP>-1</SUP> of ethanol (87.6% of theoretical yield) after 48h fermentation. Importantly, the addition of lower concentrations of exogenous nitrogen sources (3 and 6gL<SUP>-1</SUP> of yeast extract and polypeptone, respectively) or no exogenous nitrogen sources resulted in the production of 131.4 and 132.8gL<SUP>-1</SUP> of ethanol (84.8% and 86.0% of theoretical yield), respectively, after 48h fermentation.