Abstract
Viable Kluyveromyces fragi yeasts cells were successfully entrapped in polyacrylamide and kappa-carrageenan gel beads. Small amounts of precultured yeast cells were mixed with specific concentrations of gel solutions and gel beads of uniform size were manufactured by a gelation process. For both batch and continuous fermentation systems, the cells grew well in the gel. In batch fermentation trials, there was no significant shift in the pH profile for either the polyacrylamide or the kappa-carrageenan immobilized cell systems. Continuous fermentations were carried out in a column with an initial packed gel height of 13cm but with different dilution rates using 10% lactose solutions reconstituted from sweet whey powder as the medium. The immobilized growing cell systems exhibited high and stable activity for ethanol production under steady-state conditions. A maximum productivity of 7.8g/l-hr at a dilution rate of 0.800hr-l for polyacrylamide immobilized cell and 13.3g/l-hr at 0.679hr-l for kappa-carrageenan immobilized cell was obtained. Of the two methods tested, the use of kappa-carrageenan for immobilizing yeasts for ethanol production from whey was better.
