A bio-electrochemical sensor based on suspended Shewanella oneidensis MR-1 for the sensitive assessment of water biotoxicity

Abstract Water quality monitoring is important to ensure the safety of water supply. With electrochemically active bacteria (EAB) as the key element, bio-electrochemical system (BES) based biosensors are capable to detect water biotoxicity by measuring bioelectricity directly. Traditional BES biosensors relay on mature EAB biofilms. However, due to the self-protective mechanisms of biofilms, the sensitivity of BES biosensors is relatively low, and the detection limit of common pollutants was basically more than 1.0 mg/L. To solve this problem, a BES biosensor based on suspended Shewanella oneidensis MR-1 (S-BES biosensor for short) was established and was used for water biotoxicity detection. The inhibition ratio of S-BES biosensors currents achieved 11.6%-16.3% after 0.1 mg/L heavy metals or organic pollutants toxic shocks. Comparing with traditional BES biosensors, S-BES biosensors exhibited much higher sensitivity in water toxicity detection (about 30 times), showing a great prospect in source water toxicity monitoring. The mechanism of the enhanced sensitivity was further revealed, and it was mainly attributed to the relatively low resistance of suspended bacteria to toxic pollutants.