Enhancing the sensitivity of water toxicity detection based on suspended Shewanella oneidensis MR-1 by reversing extracellular electron transfer direction

Water toxicity detection is of great significance to ensure the safety of water supply. With suspended electrochemically active bacteria (EAB) as the sensing element, a novel microbial electrochemical sensor (MES) has recently been reported for the real-time detection of water toxicity, but its practical applications need to further improve the sensitivity. Extracellular electron transfer (EET) is an important factor affecting MES performance. In the study, the EET of suspended EAB-based MES was optimized to further enhance the sensitivity. Firstly, by using a model EAB stain Shewanella oneidensis MR-1, it was revealed that the sensitivity was increased at most 2.7 times with inward EET (i.e., cathodic polarization). Then, a novel conjecture based on electron transfer and energy fluxes was proposed and testified to explain this phenomenon. Finally, three key operating parameters of inward EET were orthogonally optimized. The optimized parameters of inward EET included a potential of - 0.5 V, a cell density of 1.8 x -10(8) CFU/mL, and an electron acceptor concentration of 15 mM.

Automated summary

Water toxicity detection is crucial for ensuring water supply safety. A novel microbial electrochemical sensor (MES) using suspended electrochemically active bacteria (EAB) as the sensing element has been reported, but its sensitivity needs further improvement. In this study, the extracellular electron transfer (EET) of the suspended EAB-based MES was optimized to enhance sensitivity. The optimized parameters for inward EET were a potential of - 0.5 V, a cell density of 1.8 x -10(8) CFU/mL, and an electron acceptor concentration of 15 mM.