The construction and application of an electrochemical bioreactor module will be presented as a practical tool for supplying reducing equivalents to engineered in vivo or in vitro biological systems, obviating the need to consume glucose to generate them. Thus, providing electricity from an external source to such systems offers an opportunity to significantly increase the carbon efficiencies and product yields of these processes. In fermentations, input carbonaceous material is sacrificially oxidized in order to provide electrons for downstream reductions, thus reducing the maximum theoretical carbon efficiency and yield of product. By electrochemically supplying reducing equivalents to the biological system, the stoichiometry of the chemical reaction changes so that the carbon efficiency of the biochemical reaction is improved in comparison to the case where no electrochemical reducing equivalents are provided. Though some biological systems can utilize hydrogen gas directly as a reductant, it is much more advantageous to introduce reducing equivalents as electrochemical species that are inherently compatible with aqueous biological systems. In vitro biological systems featuring processes catalyzed by enzymes stand to benefit from the electrochemical in situ regeneration of cofactors such as NAD(P)H in order to drive expensive or otherwise inaccessible biochemical reactions. Provided that electrical current can be supplied at standard industrial rates of $50-60/megawatt, it is cost-effective to generate reducing equivalents electrochemically rather than via the consumption of either 5-carbon or 6-carbon sugars at $350/metric tonne. The electrochemical bioreactor module described herein operates at a heretofore unprecedented scale, allowing for, as an example, the commercially viable electrochemical in situ regeneration of NADH for use as a cofactor to various enzymatic processes, such as the in vitro production of fatty acids using redox enzymes like P450 hydroxylase. Various other applications of this technology will also be discussed.

Utilizing electrochemical bioreactors for efficient biofuel and chemical applications

251st National Meeting (2016)

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