The hydrolysis of starch by f our Aspergillus niger strains immobilized alone or as mixture with Zymomonas nobilis in Ca-alginate beads was investigated. The hydrolisis of starch was inhibited by reducing sugars present in the medium in the amounts from 14.0 to 30.0 g/L. When strains of A niger were co-immobilized with Zymomonas mobilis, starch hydrolysis was greatly improved. The potential of the mixed cultures immobilized in Ca-alginate beads for ethanol production form starch was determined. The final concentration of ethanol produced from starch (50 g/L) ranged from 16.6 to 18.9 g/L (58.5 to 66.8% of theoretical yield).