Sodium chloride concentration determines exoelectrogens in anode biofilms occurring from mangrove-grown brackish sediment

Single-chamber microbial fuel cells (MFCs) were inoculated with mangrove-grown brackish sediment (MBS) and continuously supplied with an acetate medium containing different concentrations of NaCl (0-1.8 M). Different from MFCs inoculated with paddy-field soil (high power outputs were observed between 0.05 and 0.1 M), power outputs from MBS-MFCs were high at NaCl concentrations from 0 to 0.6 M. Amplicon-sequence analyses of anode biofilms suggest that different exoelectrogens occurred from MBS depending on NaCl concentrations; Geobacter occurred abundantly below 0.1 M, whereas Desulfuromonas was abundant from 0.3 M to 0.6 M. These results suggest that NaCl concentration is the major determinant of exoelectrogens that occur in anode biofilms from MBS. It is also suggested that MBS is a potent source of microbes for MFCs to be operated in a wide range of NaCl concentrations.