Biosensor for Direct Determination of Fenitrothion and EPN Using Recombinant Pseudomonas putida JS444 with Surface Expressed Organophosphorus Hydrolase. 1. Modified Clark Oxygen Electrode

Abstract: This paper reports a first microbial biosensor for rapid and cost-effectivedetermination of organophosphorus pesticides fenitrothion and EPN. The biosensorconsisted of recombinant PNP-degrading/oxidizing bacteria Pseudomonas putida JS444anchoring and displaying organophosphorus hydrolase (OPH) on its cell surface asbiological sensing element and a dissolved oxygen electrode as the transducer. Surface-expressed OPH catalyzed the hydrolysis of fenitrothion and EPN to release 3-methyl-4-nitrophenol and p-nitrophenol, respectively, which were oxidized by the enzymaticmachinery of Pseudomonas putida JS444 to carbon dioxide while consuming oxygen,which was measured and correlated to the concentration of organophosphates. Under theoptimum operating conditions, the biosensor was able to measure as low as 277 ppb offenitrothion and 1.6 ppm of EPN without interference from phenolic compounds and othercommonly used pesticides such as carbamate pesticides, triazine herbicides andorganophosphate pesticides without nitrophenyl substituent. The applicability of thebiosensor to lake water was also demonstrated.