Nanowire Mediated Effect of Interspecies Electron Transfer in Organic Solid Waste Co-Fermentation

Abstract

Low efficiency of Interspecific Electron Transfer (IET) among microorganisms constrains organic matter degradation and biogas production in organic solid waste co‑fermentation. This work investigates the underlying bottleneck and evaluates the nanowire‑mediated enhancement of IET. Surface plasmon resonance‑enhanced electrochemical impedance spectroscopy coupled with metagenomic and metatranscriptomic sequencing was applied to regulate endogenous nanowire formation in anaerobic reactors. Surface Plasmon Resonance-Enhanced Electrochemical Impedance Spectroscopy (SPR‑EIS) enabled real‑time quantification of interfacial charge transfer resistance, and the direct effect of nanowires on electron transfer kinetics was determined. Subsequently, by combining metagenomic and metatranscriptomic sequencing, a nanowire mediated direct IET pathway model related to the expression of key electron transfer proteins, such as the conductive pili gene‌ PilA, was constructed and validated. The experimental results showed that under magnetite induction at 4 g/L, the specific methane yield of the system reached 355.42 mL/g VS (Volatile Solids) on the 30th day. The charge transfer resistance at the microbial electrode interface decreased to 90 Ω. At the same time, the expression fold change of the conductive pili-related gene PilA increased to 4.8. The charge transfer resistance showed a significant negative correlation with the expression fold change of PilA gene (R = -0.993), confirming that the formation of nanowires directly enhances the efficiency of microbial IET.