C. saccharoperbutylacetonicum N1-4 ELECTROACTIVITY AND CO2 FIXATION UNDER DIFFERENT ELECTROCHEMICAL CONDITIONS

Abstract

The capability of certain microbial strains to uptake electrons and fix CO2 can be exploited to capture greenhouse gas and convert it into products of interest through a process called microbial bioelectrosynthesis. This study evaluated the capability of C. saccharoperbutylacetonicum N1-4 to utilize bicarbonate for growth, by both supplying electrons in a single-cell reactor and using a graphite-felt assembly as electrodes. The medium was supplemented with 4 g/L bicarbonate and 200 µM NADH. An open circuit experiment was carried out in a medium with bicarbonate and no complex nitrogen sources. The applied potential was -600 mVAg/AgCl. The impedance spectroscopy and cyclic voltammetry techniques were used to characterize and monitor the reduction and oxidation peaks. The conditions that promote the highest observed specific growth rate (0.87±0.18 h-1), were -600 mV, 4 g/L HCO3 -, and NADH. The growth rates of 0.57±0.01 h-1 were observed at 4 g/L HCO3 - without any potential input, and 0.51±0.10 h-1 at a potential of -600 mV in the presence of NADH. The results showed that an environment that provides exogenous electrons and an externally applied potential promotes the capability of C. saccharoperbutylacetonicum N1-4 to reduce CO2, as evidenced when biomass concentration and specific growth rate were increased.