Ethanol production from nonsterilized carob pod extract by free and immobilized Saccharomyces cerevisiae cells using fed‐batch culture

The production of ethanol from carob pod extract by free and immobilized Saccharomyces cerevisiae cells in batch and fed‐batch culture was investigated. Fed‐batch culture proved to be a better fermentation system for the production of ethanol than batch culture. In fed‐batch culture, both free and immobilized S. cerevisiae cells gave the same maximum concentration (62 g/L) of final ethanol at an initial sugar concentration of 300 g/L and F = 167 mL/h. The maximum ethanol productivity (4.4 g/L h) was obtained with both free and immobilized cells at a substrate concentration of 300 g/L and F = 334 mL/h. In repeated fed‐batch culture, immobilized S. cerevisiae cells gave a higher overall ethanol concentration compared with the free cells. The immobilized S. cerevisiae cells in Ca‐alginate beads retained their ability to produce ethanol for 10 days. © 1994 John Wiley & Sons, Inc.