Impact of plant-derived electron shuttles on the exoelectrogens for enhanced novel microbial desalination cell performance

Microbial desalination cells (MDC) are an emerging technology addressing wastewater treatment, energy production, and freshwater scarcity. This research aims to explore plant-derived extracts, rich in polyphenols, as mediators to improve electron transfer in MDCs. Vetiver (Chrysopogon zizanioides) and onion (Allium cepa) peel extracts were tested at different concentrations using Shewanella putrefaciens MTCC 8104 and mixed cultures as exoelectrogens. The results revealed that onion peel extract (100 µg/mL) with a mixed culture (OM-MDC) achieved the highest power density of 38.27 ± 0.7 mW/m², a 2.7-fold increase compared to controls. COD removal reached 99.2 ± 0.2 % in the vetiver-mediated mixed culture system (VM-MDC). Real-time brackish water treatment at optimized mediator concentration with OM-MDC showcased a power density of 26.85 ± 0.5 mW/m². The electrochemical analysis demonstrated a significant decrease in internal resistance and an improved expression of oxidation and reduction potentials following the addition of the mediator. Overall, plant extracts proved effective, sustainable alternatives to synthetic mediators, demonstrating potential for practical applications in seawater and brackish water treatment.