The effect of different control mechanisms on the sensitivity and recovery time of a microbial fuel cell based biosensor

Biosensors can be used detect toxicity and monitor quality of drinking water. A microbial fuel cell (MFC) based biosensor can be used to detect toxicity. Changes in water quality, as indicated by changes in cell voltage, are usually measured using an external resistance. The authors are not aware of any rationale for the choice of the magnitude of the resistance used, nor of any evidence that this method of control results in the optimal sensitivity of the sensor. The influence of the magnitude of the external resistance on the sensitivity and recovery time of the MFC-based biosensor was therefore investigated. A low resistance resulted in a large change in signal and a more sensitive sensor, while a high resistance resulted in a shorter recovery time. Furthermore, instead of an external resistor, a potentiostat was used to control anode potential or a galvanostat was used to control the electrical current. With these two types of control it was possible to detect the presence of a toxic component. A significant change in signal was observed in the sensor where anode potential was controlled. Surprisingly negative currents were also observed. When current was controlled the anode potential decreased in the presence of a toxic component as opposed to the resistor-controlled sensor in which anode potential increased in the presence of a toxic component. The recovery times of the sensors under both anode potential control and current control were found to be longer than when an external resistor was used.