Biomineralized Electroactive Microbe as the Whole-Cell Electrical Transducer for Electrochemically Online Monitoring of Lactic Acid Fermentation

Electroactive bacteria (EAB) hold great promise for the development of electrochemical biosensors given their unique ability to transfer electrons extracellularly via specialized pathways, a process termed extracellular electron transfer (EET). Ongoing research aims to overcome current limitations and fully harness the potential of EABs for high-performance biosensing applications. Herein, we report the fabrication of an electrochemical microsensor based on biomineralized electroactive bacteria, specifically Shewanella oneidensis MR-1. We exploited the EET capability of S. oneidensis to mineralize gold nanoparticles (AuNPs) in situ, thereby enhancing the EET efficiency and improving the electrochemical performance. With lactate serving as the sole electron donor, S. oneidensis functions as a whole-cell electrical transducer, converting the metabolism of lactate into detectable electrical signals. The resulting microsensor, designated AuNPs@S. oneidensis@CFE, exhibited enhanced sensitivity, a broad linear detection range, and high specificity for lactate detection, along with relatively good stability and reproducibility. Furthermore, when integrated into a three-in-one microelectrode, it enabled online monitoring of lactate fermentation. Thus, this work highlights the potential of combining the EET reduction capacity and sensory ability of EABs with miniaturized devices, demonstrating the feasibility of integrating biomineralization with EET pathways of EABs to develop robust electrochemical microbial biosensors.