Extracellular Electron Transfer Enhances Polyhydroxybutyrate Productivity in Ralstonia eutropha

Abstract

Polyhydroxyalkanoate is a biodegradable and biocompatible polymer that is synthesized in intracellular granules by a wide variety of microorganisms under growth-suppressed conditions. Herein, we report that polyhydroxybutyrate (PHB) productivity in Ralstonia eutropha was accelerated by extracellular electron transfer (EET) using a biocompatible mediator in an electrochemical system. When the electrode potential was poised at 0.6 V (vs the standard hydrogen electrode) where the EET pathway was constructed, the PHB production rate was enhanced by 60% compared to the case without the EET process. The results indicate that the extracellular anode served as an additional electron acceptor for microbial metabolism, resulting in acceleration of glycolysis and hence PHB synthesis.