Ethanolic fermentation with saccharomyces cerevisiae cells immobilized in pectate gel

High‐molecular weight pectic acid with a STAUDINGER index of 210 ml/g and a degree of esterification of 3%was used as matrix material for the immobilization of Saccharomyces cerevisiae cells. In discontinuous and continuous fermentation tests the gel beads obtained exhibited the same biomass loading capacity (152–155 g dry wt. cells/kg gel) and about the same maximum specific productivity (103.0 g ethanol/kg gel · h) as alginate immobilizates. But there were distinct differences in the swelling behaviour of the two gels. Under the same experimental conditions the increase of bead volume amounted to 27% only for pectate gel in comparison to 129% for alginate gel. In continuous fermentation experiments performed in a horizontal‐column packed‐bed reactor with liquid recycling a mean steady‐state ethanol concetration of 69.1 g/l and a mean productivity of 24.7 g ethanol/lh could be kept constant over a period of more than 10 days.