Development of a mediated whole cell-based electrochemical biosensor for joint toxicity assessment of...

Since most risk assessment for toxicants is based on individual single-species test, the deduction of such results to ecosystem evaluation is afflicted with uncertainties. Herein, we successfully developed a p-benzoquinone mediated whole-cell electrochemical biosensor for multi-pollutants toxicological analysis by co-immobilizing mixed strains of microorganism, including Escherichia coli (gram-negative bacteria), Bacillus subtilis (gram-positive bacteria) and Saccharomyces cerevisiae (fungus). The individual and combined toxicities of heavy metal ions (Cu(2+), Cd(2+)), phenol (3,5-dichlorophenol) and pesticides (Ametryn, Acephate) were examined. The experimental results showed that the order of toxicity for individual toxicant was ranked as Cu(2+) > 3,5-dichlorophenol (DCP) > Ametryn > Cd(2+) > Acephate. Then the toxic unit (TU) model was applied to determine the nature of toxicological interaction of the toxicants which can be classified as concentration additive (IC50mix = 1TU), synergistic (IC50mix < 1TU) and antagonistic (IC50mix > 1TU) responses. The binary combination of Cu(2+) + Cd(2+), Cu(2+) + DCP, Cu(2+) + Acephate, DCP + Acephate, Acephate + Ametryn were analyzed and the three kind of joint toxicity effects (i.e. additive, synergistic and antagonistic) mentioned above were observed according to the dose-response relationship. The results indicate that the whole-cell electrochemical biosensor based on mixed microbial consortium is more reasonable to reflect the joint biotoxicity of multi-pollutants existing in real wastewater, and combined effects of toxicants is extremely necessary to be taken into account in ecological risk assessment. Thus, present study has provided a promising approach to the quality assessment of wastewater and a reliable way for early risk warning of acute biotoxicity.