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° 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·^–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. Correspondence to: E. Aquarone