The aims of this study were to investigate the bioethanol production of thick juice as intermediate from sugar beet processing in batch culture by free Saccharomyces cerevisiae cells and the effect of sugar concentration on ethanol yield and CO2 weight loss rate. Thick juice and molasses of sugar beet from a domestic sugar factory were diluted with distilled water to give a total sugar concentration of 5, 10, 15, 20 and 25% (w w(-1)). Initial concentration of fermentable sugars of 20% (w w(-1)) in culture medium can be taken as optimal, enabling maximal ethanol yield (68%) and maximal CO2 evolution rate was realized, amounting to more than 90 g L-1 h(-1). The optimal concentration of fermentable sugar from thick juice for bioethanol production by free S. cerevisiae cells was 20% (w w(-1)) at 30 degrees C, PH 5 and agitation rate 200 rpm gave maximum ethanol concentration of 12% (v v(-1)). (C) 2009 Elsevier Ltd. All rights reserved.