A novel biosensor-based method for the detection of p-nitrophenol in agricultural soil

Directly measurement of the bioavailable concentration of soil contaminants is essential for their accurate risk assessment. In this study, we successfully modified and identified the key genetic elements (pobR1-3) for the bio-detection of p-nitrophenol and synthesized five novel whole-cell biosensors (Escherichia coli BL21/pPNP-mrfp, E. coli BL21/pPNP-CFP, E. coli BL21/pPNP-YFP, E. coli BL21/pPNP-GFP, and E. coli BL21/pPNP-amilCP) to directly detect the concentration of p-nitrophenol in soils. These biosensor methods contained a simple biosensor activation and sample extraction step, a cost-effective detection means, and a fast detection process (5 h) by using a 96-microwell plate with a low background value and high-reliability equation for p-nitrophenol detection. These biosensors had a detection limit of 6.21-25.2 μg/kg and a linear range of 10-10000 μg/kg for p-nitrophenol in four soils. All biosensors showed better detection performance in the detection of p-nitrophenol in soil samples. The biosensors method can help to quickly and directly assess the actual bioavailable fractions of p-nitrophenol in soils, thus facilitating to understand the environmental cycling of p-nitrophenol.