Improving the Response of Microbial Fuel Cell-Based Biosensing through Optogenetic Enhancement of Electroactive Biofilms

Early detection of pollutants in water discharge is an integral part of environmental monitoring. Electroactive biofilm (EAB)-enabled, microbial fuel cell (MFC)-based biosensors facilitate self-powered online pollutant detection. However, as EABs are highly dynamic, naturally formed EABs as sensing and transducing elements limit the performance of MFC-based biosensors. Here, we report a fast-response and sensitive MFC-based biosensor enabled by enhancing <i>Shewanella oneidensis</i> biofilms on the electrode using an optogenetic approach. We incorporated a near-infrared (NIR) light-responsive synthetic bis(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) module into <i>S. oneidensis</i> to promote biofilm formation on the anode under NIR light. The biosensors with enhanced EABs exhibited a rapid and sensitive response to Cr(VI), reducing the sensing time from approximately 30 min to just 3 min. This improved sensing performance was maintained over three sensing cycles, even with fluctuating Cr(VI) concentrations. Based on the analyses of the electrode biofilms and extracellular polymeric substance matrices, different Cr(VI) response mechanisms for the normal and enhanced EABs were proposed; enhanced EAB's massive dispersal by Cr(VI) was the cause of the improved response of the biosensors. Such improved response still held in the natural water matrix. This proof-of-concept study provides valuable insights into controlling electrode biofilm dynamics for the rapid and robust early detection of pollutants using MFC-based biosensors.