Electrotrophic microbial communities driving cathodic bioelectrochemical nitrogen and carbon fixation

The electrostimulation of complex microbial communities for biomass production represents a challenging opportunity with several industrial applications in terms of organic carbon storage and soil fertility improvement. To evaluate the biomass development induced by electrostimulation, an environmental microbial consortium was inoculated in microbial electrochemical systems (MES) where only N2 and inorganic carbon were provided. Different MES were set up as follows: constant polarization of −0.7V vs SHE, constant polarization of −0.2V vs SHE, open circuit (OC) with no polarization and abiotic control at -0.7V vs SHE. After an initial period of stabilization, the MES were run for 165 days. Preliminary results showed a higher charge accumulation and electron transfer in the inoculated systems at -0.7V polarization compared with the controls. At the end of incubation, polarized inoculated systems produced a higher biomass in the cathodic chamber compared with OC. DNA and RNA were isolated from the cathodic biofilm, the microbial suspension and the bottle wall biofilm and microbial consortia are under characterization by Illumina 16S rRNA gene sequencing and by shotgun sequencing. The outcomes from this project will provide new insights on the ecological and physiological mechanisms involved in the establishment of microbial consortia in oligotrophic environments, posing the basis for the improvement of biological nitrogen and carbon fixation to be exploited in many applications. This project is financed by project “e-Biochar” Fondazione Cariplo - Circular Economy 2019.