Thermophilic Moorella thermoautotrophica-immobilized cathode enhanced microbial electrosynthesis of acetate and formate from CO2.

Microbial electrosynthesis (MES) is a promising technique that converts electricity and CO2 to biofuels using microbes as the catalysts. However, most of previous MES are conducted at mesophilic temperatures and challenged by low performances. Here we report a significant electrosynthesis performance enhancement via immobilization of a thermophilic microbe to cathodes. A temperature-dependent electron uptake rate of Moorella thermoautotrophica was observed at a cathode potential of -0.4V (vs. SHE), with a maximum current density of 63.47mAm(-2) at 55°C. Moreover, electrosynthesis rates of formate and acetate at 55°C were accelerated by 23.2 and 2.8 fold than those of 25°C, respectively. Compared with natural biofilms, immobilization of M. thermoautotrophica with carbon nanoparticles to electrodes further enhanced acetate and formate production rates (by 14 and 7.9 fold), reaching 58.2 and 63.2mmolm(-2)day(-1) at a coulombic efficiency of 65%, respectively. To our best knowledge, these are the highest electrosynthesis rates obtained thus far for pure cultures under the conditions of -0.4V (vs. SHE) and 55°C. This study, for the first time, demonstrates that embedding microbes to electrodes by carbon nanoparticles is a facile and efficient method of improving MES performance.