Enrichment of Microbial Electrolysis Cell Biocathodes from Sediment Microbial Fuel Cell Bioanodes

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    Test tube sMFCs inoculated with (A) Harbor silt or (B) Bay sand developed exoelectrogenic activity as recorded by voltage drop across 1k Ohm external resistor (Fig. S1); consumption of electrons in Coulombs at an applied WE potential of −539 mV in PBS media degassed with N2/CO2 ratio of 80%/20% [vol/vol] after 7 days (Fig. S2); sterile control brush cathode developed no biofilm growth and cathode medium remained clear after week-long operation at applied potentials of −339 mV, −439 mV then −539 mV (Fig. S3); micrograph of Gram-stained graphite fibers recovered from the functional biocathode produced from Harbor N sample prior to 16S clone library analysis on day 61 (Fig. S4); development of negative current after transfer of biocathode inoculum, obtained from Harbor N cathode chamber on day 45, into three new BES reactors each with different cathode material (carbon fiber brush, carbon rod, or graphite plate) at an applied WE potential of −539 mV in PBS minimal media degassed with N2/CO2 ratio of 80%/20% [vol/vol] for 14 days (Fig. S5); HPLC analysis showing: sterile media (a), sterile media spiked with acetate (b), two-week-old cathode media from Bay SP reactor (c), and two-week-old cathode media from Bay N (d) (Fig. S6); electrons transferred from cathode, biogas (CH4 and H2) released to headspace, and total inorganic carbon depleted from cathode compartment over 7 day operations at applied cathode potentials of −439 mV or −539 mV vs SHE (Table S-T1); supplemental protocol: calculation of total inorganic carbon consumed.

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