A highly sensitive bioelectrochemical toxicity sensor and its evaluation using immediate current attenuation.

Electroactive biofilm (EAB) sensor had shown great potential in the field of early warning of toxicants in water because of the low-cost and broad-spectrum. However, the traditional calculation of sensitivity strongly relied on the time and concentration gradient which weakened time-efficiency of the sensor. Moreover, the sensitivity could be further improved to respond trace concentrations. Here EAB sensors with different substrate concentrations were formed to respond different concentrations formaldehyde ranging from 1 ppm to 50 ppm and immediate current attenuation (ICA) was induced to evaluate the sensitivity. The ICA (~70 s) exhibited a shorter time than that calculated by calculable sensitivity (CS) and current attenuation (CA), which not only achieved the response of trace concentration but also improved the time-efficiency of the sensor. The EAB formed with 0.1 g/L acetate (EAB-0.1) had a 380% higher sensitivity than that formed with 1.0 g/L acetate (EAB-1.0), leading to a significant electrochemical toxicity response to 1 ppm of formaldehyde. The results of electrochemical response coefficient confirmed that EAB-0.1 was 1.5-6.3 times of that formed with acetate from 0.2 to 1.0 g/L, which was related with microbial community and component of EAB as described in our previous study. Our findings demonstrated that calculation of sensitivity could be optimized to reflect time-efficiency and EAB with limit acetate could be applied in trace toxicant detection.