[Production of ethanol by fermentation with a high concentration of yeasts. Its application in already installed...

Due to the dramatic increase in international oil prices, the ethanol production by fermentation is presently becoming an attractive and feasible project for many countries Argentina has implemented an experimental national program of ethanol use as fuel and the standard procedure of Melle-Boinot is currently employed in sugar cane molasses fermentation. The aim of this work was to improve the overall efficiency of the batch process by recycling high levels of yeast biomass. It was observed that the volumetric productivity increased with biomass concentration, whereas the specific productivity decreased. Both variations were not linear (Fig. 1). It was difficult to keep a yeast concentration higher than 3 x 10(8) cell/ml during batch fermentation assays. Anyhow the periodic subculturing of yeast biomass (every 13 recycling periods) proved to be an effective method to obtain a high cell density in the fermentation medium (Fig. 2). The industrial application of data reported here would not imply additional investment or equipment to distilleries using standard fermentation procedures.