Transmembrane electron transfer for microbial CO2 conversion using periplasmic gold nanoparticles

Microbial electrosynthesis can convert CO 2 into useful chemicals, but electron transport across the cell envelope remains a major limitation. Here, we introduce periplasmic gold nanoparticles (AuNPs) in Ralstonia eutropha to facilitate transmembrane electron transfer during CO 2 conversion. The AuNPs reduce interfacial charge-transfer resistance by more than 95%, enabling more efficient delivery of electrode-derived electrons into cellular metabolism. As a result, the biohybrid system shows markedly improved CO 2 reduction performance. Product selectivity can be tuned through bioelectrode design: drop-casted electrodes favor acetate production, whereas self-assembled biofilms achieve over 90% selectivity for C 4 products, with a maximum Faradaic efficiency of 44.4%, reaching 71% of the theoretical limit for aerobic CO 2 fixation. Spectroscopic, electrochemical, and transcriptomic analyses support enhanced electron transfer and carbon metabolism. This work provides a practical strategy for wiring non-electrogenic microbes and improving microbial CO 2 conversion to multi-carbon chemicals.