Powering fermentations with electroactive microbes

In Nature, highly efficient and diverse microbial consortia process waste organic matter to generate energy for growth, simultaneously recycling carbon and other vital elements. Driving these reactions are organisms with the ability to extract electrons from the chemical substrates and transfer them to redox-active minerals. One group in particular, Geobacter bacteria, can couple their metabolism to the reduction of insoluble minerals such as iron and manganese oxides. We show that this natural process can be mimicked in reactors equipped with bioelectrodes, which stack the electrochemically active cells on electrodes and harvest an electrical current from waste fermentation byproducts. The synergistic interactions between fermentative bacteria and the bioelectrode in the electrochemical reactors enable the efficient processing of waste substrates such as corn stover and biodiesel glycerin into alcohol fuels and chemical precursors while enriching for the added-value product in the broth, thus reducing the cost associated with downstream separation steps. In addition, the electricity generated by the bioelectrode is used to generate hydrogen fuel at the cathode.