Double-edged sword effects of platinum-coated cathodes on methane production pathways in microbial electrolysis cell-coupled anaerobic digestion systems.
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75% confidenceThe use of platinum-coated cathodes in microbial electrolysis cell-anaerobic digestion systems exhibits a double-edged sword effect, enhancing methane yield but also inhibiting certain methanogenesis pathways. The highest methane yield was achieved at 0.8 V, with a yield of 445.71 mL/gCOD. However, the overall enhancement was limited due to the inherent biotoxicity of platinum-coated cathodes.
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Abstract
Although platinum-coated cathodes (Pt-C) are commonly applied in microbial electrolysis cell-anaerobic digestion (MEC-AD) systems for methanogenesis, they exhibit inherent biotoxicity. At 0.8 V, Pt-C achieved the highest methane yield (445.71 mL/gCOD), but overall enhancement remained limited. This treatment enhanced inter-biofilm electron transfer processes and electrolyte transport, particularly at cathodes, thereby stimulating quorum sensing, proteolysis, amino acid/peptide transport, and acidification of substrates. It promoted the proliferation of cathodic unclassified_f_Methanobacteriaceae and Geobacteraceae, upregulated hmd, acs and coo, which drove hydrogenotrophic methanogenesis, acetoclastic methanogenesis, and syntrophic acetate oxidation via direct interspecies electron transfer. Conversely, it inhibited formate and methylotrophic methanogenesis pathways and associated genes. Notably, methylotrophic methanogens, despite low abundance, had a disproportionately significant role in methane production. These findings underscore Pt's "double-edged sword" effect, revealing its complex, selective influence on microbial metabolism and methanogenic pathways in MEC-AD systems, providing novel mechanistic insights into optimizing CH 4 production.