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... it.org/fr/usagers/politique-dutilisation/ Document téléchargé le 13 février 2017 02:40 REVUE DES SCIENCES DE L'EAU, 5(1992) 445-461 Biocapteurs pour le contrôle de la toxicité des eaux : application des bioélectrodes algales Biosensors for monitoring pollutions of aquatic Systems : applications of algal électrodes PASCAL PANDARD1.PAULE VASSEUR1 Reçu le 17 juin 1991, accepté pour publication le 4 mars 1992". SUMMARY Environmental monitoring of poMutants with automatic Systems, applied online and allowing rapid response constitutes one of the most successful ways to improve the quality of the environment. Real time analysis offers the advantage of detecting rapidly sources of pollution and preventing any accidentai release of pollutants. Such a strategy is possible only by means of biosensors : current methods, commonly used for toxicity testing are usually carried out in laboratory in static conditions, maxing real time analysis impractical. Two types of amperometrjc environmental sensor incorporating eukaryotic algae were investigated for use in monitoring industrial pollution of aquatic Systems. Both sensors allowed the monitoring of photosynthetic events. The first sensor follows photosynthetic électron chain events within the cell resulting in the réduction of mediator acting as terminal électron acceptor. Reoxidation of the mediator at the biosensor électrode surface results in a flow of current, the magnitude of which is proportionai to the level of photosynthetic activity of the microalgae. In the second approach photosynthetic oxygen évolution by the illuminated biocatalyst is measured by réduction at a cathodic électrode. Enzymic Systems associated with the water splitting and oxygen évolution are amongst the most fragile components of the photosynthetic apparatus, and the monitoring of algal oxygen production is therefore a useful approach to earty détection of toxie environmental pollutants. Several species of unicellular algae were used for thèse experiments : Chloreila vulgaris, Scenedesmus subspicatus and Selenastrum capricornutum. Algal cultures were harvested in the exponential growth phase and 1. Laboratoire de toxicologie. Centre des Sciences de l'Environnement 1, rue des Récollets, BP 4025,57040 Metzcedexl. REVUE DES SCIENCES DE L'EAU, 5<3), 1992 P. Pandard et P. Vasseur diluted to 0.5 O.D. (665 nm) ; then 1 ml aliquots were centrifuged at 900xg for 3 min. After centrifugation, cells were resuspended in growth médium, LEFEBVRE and CZARDA (LC), and immobilized by aspiration onto a filter dise. This filter dise was placed onto the carbon working électrode surface. Fillers were held in place by a fine nylon mesh. This biosensor is a two électrode System comprising a carbon working électrode and Ag/AgCI referen ce/cou nier électrode. Solution was continuously flowed through the electrochemical cell at a flow rate of 2 mt min -1 . Illumination of the algal biocatalyst was supplied by light emitting diodes with a peak wavelength of 635 nm and a light intensity of 125 milticandeflas. Periodicity flf illumination was chosen in order to obtain a stable photosynthetic response.