Hibernations of electroactive bacteria provide insights into the flexible and robust BOD detection using microbial fuel cell-based biosensors

Highlights: • EAB hibernation enables flexible and robust BOD detection using MFC biosensors. • Identical anode potential suggests intact bacterial activity after EAB hibernation. • Non-turnover CV revealed multiple redox couples and presence of cytochromes in EAB. • EAB capacitance contributed to the increased BOD detected in the restarting cycle. Microbial fuel cell (MFC) biosensors have been suggested as an alternative detection method for biochemical oxygen demand (BOD). However, it is absolutely essential to develop maintenance procedures for MFC biosensors because in practice the lay-up period cannot be avoided. In this work, setting electroactive bacteria (EAB) under hibernation condition was demonstrated to be a feasible maintenance method, which provided important insights into the flexible and robust BOD detection using MFC biosensors. Standard BOD solution containing 500, 200, and 20 mg/L BOD were used to evaluate the detection performance after EAB hibernations. Results demonstrated quick recovery of voltage output and high-accuracy BOD detection after hibernations up to 30 days in MFC biosensors detecting 500 mg/L and 200 mg/L BOD. Identical anode potentials after the EAB hibernations suggested intact bacterial ability of current generation. Non-turnover cyclic voltammetry immediately collected after the hibernations suggested multiple redox couples and the presence of cytochromes that played key roles in EAB metabolism and functioned as temporary electron sinks during the hibernations, leading to the increased detected BOD concentration in the restarting cycles. Generally, setting EAB under hibernation condition is a simple and convenient maintenance method for MFC-based BOD biosensors, which not only provides insights into flexible and robust BOD detection, but also be helpful for other MFC biosensing instruments.