Effect of cathode properties on the thermophilic electrosynthesis of PolyHydroxyAlkanoates by Kyrpidia spormannii

The recent discovery of the Knallgas bacterium Kyrpidia spormannii EA-1, able to produce PolyHydroxyAlkanoates (PHAs) on a cathode, is of great interest to produce bioplastics from electricity and CO2 waste streams. However, little is known on how to improve its electroautotrophic growth and performance in PHA production. We investigated the effect of cathode properties on biofilm formation and PHA synthesis, focusing on the choice of cathode material, the surface modification of a graphite cathode with different treatments or by electrodeposition of metal catalysts, and the distance between anode and cathode. The results show higher performance of iron-based electrodes, isopropanol and sonication treatment, and close distance between electrodes, with up to a 3-fold increase of PHA production, reaching a production of 117 mg·day−1·m−2, and a 10-fold increase in cell density of the biofilm (10.7 Log10 cells·cm−2).