Ethanol production from cellulose by a coculture of Zymomonas mobilis and a clostridium

Zymomonas mobilis and a mesophilic cellulolytic clostridium (strain C7) were grown in coculture in a medium containing cellulose as fermentable substrate. The coculture was stable through at least ten serial transfers and produced markedly higher amounts of ethanol than monocultures of the cellulolytic clostridium. Glucose and cellobiose, derived from the breakdown of cellulose, accumulated in strain C7 monocultures, but not in cocultures. The molar ratio of ethanol to acetate was higher in cocultures than in monocultures of strain C7. The cellulolytic clostridium was relatively ethanol-tolerant, inasmuch as it grew and fermented cellulose in media containing up to 7 g of ethanol/100 ml. Cellulase (Avicelase) activity of strain C7 was inhibited by cellobiose, but not by glucose. 18 references, 4 figures, 4 tables.