Biocathodes reducing oxygen in BPE-ECL system for rapid screening of E. coli O157:H7

After discovery of electron transfer from bacteria, most bacteria known to be electrochemically active are utilized as a self-regenerable catalyst at the anode of microbial fuel cells (MFCs). However, the reverse phenomenon, cathodic catalysts is not so widely researched. This present study demonstrated that E. coli O157:H7 was electrochemically active, and it was able to catalyze oxygen reduction at the cathode of bipolar electrode (BPE). Applying a constant potential to the BPE, E. coli O157:H7 can catalyze electrochemical reduction of O-2, decrease the overpotential of O-2 reduction at the cathode, which in turn generates an electrochemiluminescence (ECL) reporting intensity change at the anode. Significantly, a majority of food matrix does not exhibit catalytic activity for electrochemical reduction of O-2. Meanwhile, due to the physically separation of two poles of closed BPE, complex food matrix at the cathode does not interfere with the ECL reaction at the anode. Therefore, the effect of food matrix is negligible when measuring E. coli O157:H7 levels in food. A low detection limit of 10 CFU mL(-1) E. coli O157:H7 could be identified within 1 h. Thus, biocathodes reducing oxygen in BPE-ECL system has shown excellent characteristics in the field of rapid detection of electroactive bacteria in food.

Automated summary

This study demonstrates that E. coli O157:H7 can electrochemically catalyze oxygen reduction at the cathode of bipolar electrode (BPE), resulting in electrochemiluminescence (ECL) reporting intensity change at the anode. Most food matrix does not exhibit catalytic activity for electrochemical reduction of O-2, and their interference with the ECL reaction at the anode is negligible. A low detection limit of 10 CFU mL(-1) for E. coli O157:H7 can be achieved within 1 hour using this system, making it an excellent tool for rapid detection of electroactive bacteria in food.