Potential for use of a cyanobacterium Synechocystis sp. immobilized in poly(vinylalcohol): Application to the detection of pollutants

A cyanobacterium, Synechocystis sp. PCC 6803, was immobilized by entrapment in poly(vinylalcohol) bearing styrylpyridinium groups. Its properties in a single-compartment micro-photoelectrochemical cell using platinum electrodes in potentiosatic mode were compared with the native material. The operational activity was measured in the presence of an electrolytic solution containing 20 mM sodium phosphate, 0.15 mM NaCl and 1 mM MgCl₂. The best conditions of use are pH 7.0, 38 °C and a 2,5-dichlorobenzoquinone concentration equal to 350 M with native cyanobacteria or pH 6.5, 25 °C and 500 M 2,5-dichlorobenzoquinone after entrapment. Using this procedure, the photocurrent could be inhibited by pollutants such as Diuron or HgCl₂. After entrapment, the detection limits (corresponding to a 10% inhibition) were respectively 0.5 M and 50 M for Diuron and HgCl₂ after five minutes of incubation. A permeabilization technique was used to increase sensitivity of the procedure to the detection of HgCl₂ (25% inhibition with 50 M after five minutes of incubation).