Abstract

Butanol is a strong candidate to replace fossil fuels and its biological production has been intensively researched. The ABE (Acetone-Butanol-Ethanol) fermentation, performed by Clostridium acetobutylicum, is a process that involves a metabolic shift where both carbon and reducing power (NADH) are redirected from the production of acids to the production of solvents. The supplementation of butyrate would decrease production of butyric acid which would increase the production of solvents. Since the production of solvents is related to the availability of NADH and considering that neutral red has a redox potential lower than NAD+/NADH, its reduced form (by an external power supply) can act as an electron carrier increasing the concentration of NADH. On this basis we hypothesized that the supplementation of butyrate to the culture medium and an external electron carrier acting as a co-reducing agent, along with glucose-derived reducing power (electrofermentation, EF), would increase the production of butanol; which is the aim of this work.