Investigating substrate impact on electroactive biofilm performance in low-cost, single-chamber microbial electrolysis cells for biosensing†

Abstract

Increasingly rigorous environmental regulations along with advances in water technology and policy are driving a growing need for real-time, online water quality monitoring. Recent advances in bioelectrochemical systems (BESs) open their possible use as biosensors, given their operational ease, adaptability, and cost-effectiveness. There remain, however, significant research gaps in both simplifying and reducing the costs of these systems while also testing their application with representative water matrices and substrates that would advance their use towards practical applications. This study compared the performance of single-chamber microbial electrolysis cells (SCMECs) when subjected to different substrate compositions and strengths, and their consequent capacity to quantify acetate and chemical oxygen demand (COD). Bench-scale batch and continuously fed experiments were conducted over a period of 113 d, where MECs were fed a synthetic domestic wastewater with either acetate or a complex mixture of biopolymers as their electron source. MEC current production had a strong linear relationship with acetate concentration, and MECs initially fed acetate exhibited a greater linear range of acetate detection up to 100 mg L⁻¹ compared to 40 mg L⁻¹ for MECs initially fed complex substrates. Microbial community analysis revealed higher relative activity of the model exoelectrogen, Geobacter spp., in MEC biofilms fed acetate (up to 91%) compared to those fed complex substrates (23–39%). MECs fed complex substrates also featured a more diverse community (inverse Simpson diversity = 6.36–9.87) compared to MECs fed acetate (1.22–2.03). This study suggests that the linear range of detection for MEC biosensors is improved with higher Geobacter spp. activity and when acclimated with the substrate of their intended application.