FED-BATCH ALCOHOLIC FERMENTATION OF SUGAR-CANE BLACKSTRAP MOLASSES - INFLUENCE OF THE FEEDING RATE ON YEAST YIELD AND PRODUCTIVITY

Fed-batch ethanol fermentation tests of sugar cane blackstrap molasses were carried out at 32-degrees-C and pH 4.5-5.0, using pressed yeast as inoculum, and with no air supply. Two values of the fermentor filling-up time were adopted: 5 h and 7 h. The feeding rates obeyed equation F = F0 . e(-K.t), with K equal to 0.0, 0.2, 0.4, 0.6 and 0.8 h-1. The average yeast yields and the average yeast productivities increased up to 33% and 45%, respectively, while the ethanol yield (average = 76%; standard deviation = 4%) was practically unaffected when K increased from 0 to 0.8 h-1.