A MICROSENSOR FOR NITRATE BASED ON IMMOBILIZED DENITRIFYING BACTERIA

A biosensor for NO3- was constructed by attaching a 30- to 70-mu m-wid e capillary with immobilized denitrifying bacteria in front of an N2O microsensor, These bacteria reduced O-2 so that only bacteria in the v ery tip of the sensor were exposed to O-2 whereas bacteria at a greate r depth could carry out the anaerobic process of denitrification, In t he presence of acetylene, which inhibits nitrous oxide reductase, bact eria reduced NO3- (or NO2-) from the surrounding medium to N2O and the concentration sensed by the N2O microsensor was directly proportional to the concentration of NO3- in the medium. By applying a 250-mu m-lo ng capillary in front of the N2O microsensor, the 90% response time of the biosensor was 50 s, Biosensors may also be made with nitrous oxid e-deficient strains so that acetylene inhibition can be omitted.