A SENSITIVE PHOTOSYSTEM II-BASED BIOSENSOR FOR DETECTION OF A CLASS OF HERBICIDES

We have developed a biosensor for the detection of residual triazine-, urea- and phenolic-type herbicides, using isolated photosystem II (PS II) particles from the thermophilic cyanobacterium, Synechococcus elon gatus, as biosensing elements. The herbicide detection was based on th e fact that, in the presence of artificial electron accepters, the lig ht-induced electron transfer through isolated PSII particles is accomp anied by the release of oxygen, which is inhibited by the herbicide in a concentration-dependent manner. The PSII particles were immobilized between dialysis membrane and the Teflon membrane of the Clark oxygen electrode mounted in a flow cell that was illuminated. Inclusion of t he antibiotic chloramphenicol in the reaction mixtures prolonged, by 5 0%, the lifetime of the biosensor. The use of highly active PSII parti cles in combination with the flow system resulted in a reusable herbic ide biosensor with good stability (50% of initial activity was still r emaining after 35-h use at 25 degrees C) and high sensitivity (detecti on limit for diuron was 5 x 10(-10) M). (C) 1998 John Wiley & Sons, In c.