Co-production of bioelectricity and butanol by engineered Escherichia coli fed organic wastes in anodic fermentation

Abstract

Electrofermentation improves the performance of microbes cultured on organic byproducts such as glycerol or acetate by supplementing cofactors or resolving cofactor imbalances. By employing Escherichia coli as the candidate microbe in electrofermentation, its broad product range, ease of genetic manipulation and predictable performance in both aerobic and anoxic conditions can be leveraged. Here, we demonstrate anodic electrofermentation for simultaneous production of electricity and the biofuel butanol, using engineered electroactive E. coli grown on organic byproducts. Relative to glucose as carbon source, acetate produced mainly electrical current achieving ∼80% of the electron output of glucose plus some butanol. Glycerol was the most effective carbon source tested for the engineered system resulting in the highest delivery of electrons and the highest butanol production. Increasing glycerol concentration and electrode surface area commensurately increased electron output without decreasing butanol production. Accordingly, E. coli can be applied more widely in electrofermentation to deliver a wide range of chemicals and electrons using waste byproducts as carbon feedstocks.