Although numerous studies have examined many of the factors that affect the efficiency of batch ethanol fermentation, little attention has been paid to the influence of the biomass concentration on this efficiency. This paper shows that the influence of the biomass initial concentration on the fermentation efficiency depends on what is considered "produced ethanol". If only the ethanol present in the medium aqueous phase at fermentation completion is considered, the fermentation efficiency linearly decreases when the biomass initial concentration increases. If, however, the intracellular ethanol is also considered as produced ethanol, the fermentation efficiency is not affected by the biomass concentration.
ethanol fermentation efficiency; intracellular ethanol; biomass concentration
