Electricity production and key exoelectrogens in a mixed-culture psychrophilic microbial fuel cell at 4 °C.

The electricity production via psychrophilic microbial fuel cell (PMFC) for wastewater treatment in cold regions offers an alternative to avoid the unwanted methane dissolution of traditional anaerobic fermentation. But, it is seldom reported by mixed-culture, especially closed to 0 °C. Thus, a two-chamber mixed-culture PMFC at 4 °C was successfully operated in this study using acetate as an electron donor. The main results demonstrated a good performance of PMFC, including the maximum voltage of 513 mV at 1000 Ω, coulombic efficiency of 53%, and power density of 689 mW/m2. The cyclic voltammetry curves of enriched biofilm showed a direct electron transfer pathway. These good performances of mixed-culture PMFC were due to the high psychrophilic activity of enriched biofilm, including exoelectrogens genera of Geobacter (6.1%), Enterococcus (17.5%), and Clostridium_sensu_stricto_12 (3.8%). Consequently, a mixed-culture PMFC provides a reasonable strategy to enrich exoelectrogens with high activity. For low-temperature regions, the mixed-culture PMFC involved biotechnologies shall benefit energy generation and valuable chemical production in the future. KEY POINTS: • PMFC showed a maximum voltage of around 513 mV under a resistance of 1000 Ω. • The coulombic efficiency was 53% and the max power density was 689 mW/m2. • Geobacter, Enterococcus, and Clostridium_sensu_stricto_12 were key exoelectrogens.