A novel biosensing system for rapid and sensitive detection of heavy metal toxicity in water.

Toxicity biosensors have recently gained significant attention due to their potential use in online monitoring. However, the effects of toxicants and the influence of dose, exposure time, and type and concentration of respiration substrate (RS) on the performance of a bioreactor are species-specific. Although these factors need to be investigated case-by-case as they can lead either to damage or self-repair of the affected microorganisms, they have seldom been considered in previous studies. Therefore, this work examined, for the first time, the effects of resting time and RS concentration on the performance of the biosensing system for toxicity of Cr6+ in water. In addition, it is also the first time that a novel non-contact fluid delivery system was applied to a toxicity biosensing system to prevent unstable responses. By choosing the best RS concentration and balancing the resting and exposure times, the proposed procedure exhibits promising results in terms of minimum detectable concentration (MDC), limit of detection (LOD), detection range, linearity, sensitivity, reproducibility and accuracy. The recovery time was only a few hours and the coefficients of variation of inhibition and recovery were only 12% and 9.6%, respectively, during six times reuse over one month of storage.