A mixed continuous culture of Clostridium butyricum and Enterobacter aerogenes removed O-2 in a reactor and produced H-2 from starch with yield of more than 2 mol H-2/mol glucose without any reducing agents in the medium. Co-immobilized cells of the bacteria on porous glass beads evolved H-2 from starch at 1.3 l/l.h, with H-2 yield of 2.6 mol H-2/mol glucose at dilution rate of 1.0 h(-1) in a continuous culture.