(239d) Engineering Escherichia coli for Direct Ethanol Production from Cellobionate

In our previous work, a novel biochemical route for fuel and chemical production from cellulose was proposed. Instead of producing sugars as the intermediate, a sugar aldonate (cellobionate) was produced for subsequent fermentation. We have demonstrated that cellobionate can be produced by an engineered strain of the cellulolytic fungus Neurospora crassa. The hydrolysate, comprised mainly of cellobionate (a dimer of glucose and gluconate), can be fermented into ethanol and acetate by an engineered E. coli KO11 strain, which bears an ethanol production pathway from Zymomonas mobilis.  Modifications to competing pyruvate pathways enabled ethanol yields at 97.5% of the theoretical maximum when grown on gluconate. In order to directly make use of the product of the N. crassa cellololysis, this strain was then further modified to enable anaerobic cellobionate fermentation. The strain engineering and fermentation of cellobionate to ethanol data will be reported.