Electron carriers increase electricity production in methane microbial fuel cells that reverse methanogenesis

Table 1 Maximum voltage (mV) in the MFC reactors

MFC reactor	Maximum voltage (mV)
Base case #1	670 ± 60
Trace element solution (1× → total 5×) with G. metallireducens	272
Vitamin solution (1× → total 5×) with G. metallireducens	275
Cysteine–HCl (3.2 mM → total 16 mM) with G. metallireducens	524
Na₂S (1 mM → total 5 mM) with G. metallireducens	649
Base case #1 without cysteine–HCl	757
Base case #1 + sodium acetate (10 mM)	562
Base case #1 + D. vulgaris	622
Base case #1 + Baar’s medium	623
G. metallireducens	641.0 ± 0.7
Base case #1 + G. metallireducens (mix of G. sulfurreducens and G. metallireducens)	158
Base case #1 + cytochrome C from equine heart (20 µM)	500 ± 200
Base case #1 + cytochrome C from S. cerevisiae (20 µM)	690 ± 70
Base case #1 + humic acids (0.5%)	660 ± 60
G. sulfurreducens at start then sludge + M. acetivorans (base case #2)	721.5 ± 0.7
Base case #1 with a Pt wire anode	663 ± 7

Base case #1 is M. acetivorans AA/pES1MAT mcr3 (“M. acetivorans”) and G. sulfurreducens added first followed by sludge once the voltage was below 150 mV. G. metallireducens replaced G. sulfurreducens upon inoculation. Sodium acetate (10 mM) was added to the base case #1 with sludge. D. vulgaris, Baar’s medium, and G. metallireducens, and were added to the base case #1 after it reached the maximum voltage. Cytochrome C from equine heart (20 µM), cytochrome C from S. cerevisiae (20 µM), and humic acids (0.5%) were added to the base case #1 with sludge. Base case #1 was altered by adding G. sulfurreducens at the start then adding sludge + M. acetivorans once the voltage was reduced to 150 mV. The anode electrode was replaced by Pt wire (surface area 1 × 10⁻⁵ m²). The cathode electrode diameter was 38 mm (surface area is 0.00227 m²). The external resistance was 1000 Ohm

ISSN: 2731-3654