Bioethanol Production by Repeated Batch Using Immobilized Yeast Cells on Sugarcane Bagasse

Delignified sugarcane bagasse from the sugar industry was used as a carrier for Saccharomyces cerevisiae SC90 immobilization and ethanol production. The proficiency of cell immobilization of S. cerevisiae SC90 on delignified sugarcane bagasse was determined by the amount of cell retention on the carrier and by scanning electron microscopy (SEM). S. cerevisiae SC90 showed the highest cell immobilization on day 1 when diluted molasses (231 g/L of total sugar) was used as a substrate. The efficiency of ethanol production by the immobilized cells was compared with cells grown in suspension in the repeated batch process. Immobilized cells exhibited a higher ethanol production than the suspended system for all five consecutive batches without any requirement for cell adaptation. The maximum ethanol yield (Y-P/S) of the immobilized cells was 0.42 +/- 0.02 g/g (82.35% theoretical yield) in a 3 L packed bed bioreactor when the production could be prolonged up to five consecutive batches. As an additional bonus, the high protein spent yeast cells mixed with delignified sugarcane bagasse can be explored as an animal feed in the future.