Amplifying the electron transfer process in a microbial electrolysis cell using reduced graphene oxide, Geobacter sulfurreducens and encapsulated Pseudomonas aeruginosa

This study evaluates how encapsulating Pseudomonas aeruginosa, a redox-phenazine mediator-producing bacterium, enhances the performance of microbial electrolysis cells (MECs) when combined with reduced graphene oxide (rGO) and Geobacter sulfurreducens. Two encapsulation approaches were compared: a dialysis bag and a cellulose acetate capsule were evaluated for controlled phenazine release, confirmed by UV-Visible, FT-IR, and HR-MS analyses. The capsule-based system improved mass transfer, enabling efficient diffusion of redox mediators to the rGO-biofilm interface, thereby enhancing electron shuttling, reducing charge-transfer resistance, and supporting metabolically active biofilms. MECs were operated with rGO concentrations at 0.2 and 0.4 mg/mL. At 0.2 mg/mL, rGO enhanced current density by 20-30% across all configurations, with the highest value observed in the GS-CAP (PA)-rGO system (2.5 ± 0.5 A/m²). Increasing rGO concentration to 0.4 mg/mL further improved the current density (3.22 ± 0.34 A/m²) and reduced R_ct, indicating enhanced electron transfer. MTT assay and SEM analysis confirmed enhanced biofilm formation and bacterial viability. COD removal was 76.6 ± 1.8%. Raman spectroscopy indicated strong interactions between rGO and G. sulfurreducens, confirming improved MEC performance. These findings demonstrated a promising strategy to enhance electron transfer in MECs, which will contribute to the development of efficient technologies for wastewater treatment and hydrogen production.