Oxygen-reducing microbial cathodes in hypersaline electrolyte

Hypersaline electrolytes offer a way to boost the development of microbial fuel cells by overcoming the issue due to the low conductivity of the usual media. Efficient halotolerant bioanodes have already been designed but O₂-reducing cathodes remain a strong bottleneck. Here, O₂-reducing biocathodes were designed by using salt marsh sediment as the inoculum and a hypersaline media (45 g/L NaCl) of high conductivity (10.4 S m^-1). Current density up to 2.2 A m^-2 was reached from potential of +0.2 V/SCE. The efficiency of the biocathodes was correlated to the presence of Gammaproteobacteria strain(s) related to Thiohalobacter thiocyanaticus, which were considerably enriched in the best performing biocathodes. This work opens up new perspectives to overcome the O₂ reduction issue in hypersaline MFCs by designing efficient halotolerant microbial cathodes and pointing out the strains that should now be focused to improve them.