Geobacter sp. SD-1 with enhanced electrochemical activity in high-salt concentration solutions

Summary: An isolate, designated strain SD-1, was obtained from a biofilm dominated by Geobacter sulfurreducens in a microbial fuel cell. The electrochemical activity of strain SD-1 was compared with type strains, G.sulfurreducensPCA and Geobacter metallireducensGS-15, and a mixed culture in microbial electrolysis cells. SD-1 produced a maximum current density of 290±29Am^-3 in a high-concentration phosphate buffer solution (PBS-H, 200mM). This current density was significantly higher than that produced by the mixed culture (189±44Am^-3) or the type strains (<70Am^-3). In a highly saline water (SW; 50mM PBS and 650mM NaCl), current by SD-1 (158±4Am^-3) was reduced by 28% compared with 50mM PBS (220±4Am^-3), but it was still higher than that of the mixed culture (147±19Am^-3), and strains PCA and GS-15 did not produce any current. Electrochemical tests showed that the improved performance of SD-1 was due to its lower charge transfer resistance and more negative potentials produced at higher current densities. These results show that the electrochemical activity of SD-1 was significantly different than other Geobacter strains and mixed cultures in terms of its salt tolerance.