Batch and continuous glycerol fermentations of sugar beet molasses have been studied using sulphite as a combining agent with the aldehyde function. The processes were carried out in a vertical packed-bed reactor with Saccharomyces cerevisiae yeast cells immobilized in sintered glass rings. The influence of sulphite dosage and the dilution rate on the performance of the bioreactor was studied. A maximum glycerol concentration of 30 g dm-3 and a productivity of 36.6 g dm-3 d-1 at T = 28-degrees-C, pH = 6.9 with 25 g dm-3 sodium sulphite, for a dilution rate of 1.22 d-1, was achieved.