Co-immobilization of Aspergillus niger and Zymomonas mobilis for ethanol production from starch

The hydrolysis of starch by four Aspergillus niger strains immobilized alone or as mixture with Zymomonas nobilis in Ca-alginate beads was investigated. The hydrolysis 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).