For continuous production of ethanol from thinned corn starch as substrate, two bioreactors were coupled: a column reactor filled with glucoamylase covalently immobilized on a polyacrylamide bead support containing carboxylic groups activated by a watersoluble carbodiimide, and a vertical reactor segmented with perforated plates supporting Saccharomyces cerevisiae cells entrapped in calcium alginate gel beads. The immobilized glucoamylase reactor produced a solution containing 217.1 +/- 17.4 g dm-3 of glucose. The operation of the reactor system was characterized by an ethanol concentration of 38.8 +/- 0.3 g dm-3, a fermentation efficiency of 84.5 +/- 4.1% and a volumetric productivity of 1.40 +/- 0.12 g dm-3 h-1.