Ethanol fermentation of whey using polyacrylamide and kappa-carrageenan entrapped yeasts.

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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 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 the polyacrylamide or the .kappa.-carrageenan immobilized cell systems. Continuous fermentations were carried out in a column with an initial packed gel height of 13 cm 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 7.8 g/l-h at a dilution rate of 0.800 h-l for polyacrylamide immobilized cell and 13.3 g/l-h at 0.679 h-l for .kappa. carrageenan immobilized cell was obtained. Of the 2 methods tested, the use of .kappa.-carrageenan for immobilizing yeasts for ethanol production from whey was better.