Effect of Electroactive Biofilm Formation on Acetic Acid Production in Anaerobic Sludge Driven Microbial Electrosynthesis

Microbial electrosynthesis (MES) is a biocathode driven production of value added platform chemicals from carbon dioxide (CO₂), which is regarded as a sustainable carbon mitigation approach. In this technique, electrons are supplied from external sources and subsequently utilized by the microorganisms present in the MES cathode for converting CO₂ into useful chemicals (i.e. acetic acids, butyric acid, propanol, ethanol, etc.). However, the performance of MES severely depends on the formation of an electroactive biofilm with the ability of paramount charge discharging properties. In the present work, we have investigated the influence of electroactive biofilm formation on the performance of acetic acid production in an anaerobic sludge driven MES system. The formation electroactive biofilm on the MES biocathode was characterized using different electrochemical techniques, such as chronoamperometry, linear sweep voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy, and correlated with the performance of acetic acid production. The electrochemical results demonstrated that the formation of mature electroactive biofilms on biocathodes enabled a maximum 36.66 mmol/L of acetic acids. Furthermore, the influence of different applied potentials on electroactive biofilm formation as well as acetic acid production was investigated, and it was observed that the applied potential of −0.68 V achieved maximum reducing current and acetic acid production together with maximum CO₂ consumption. The phylogenetic analysis of cathode biofilm revealed that Burkholderiales sp., Sulfurospirillum sp., Acetoanaerobium sp., and Lysinibacillus sp. were the predominant microbial genera associated with the electrosynthetic reactions in MES systems. The results of the present study suggest that the formation of an electroactive biofilm enriched with electrosynthetic genera is beneficial to avail maximum performance in MES systems.