Entrapment of chloroplasts and thylakoids in polyvinylalcohol-SbQ. Optimization of membrane preparation and storage conditions

Chloroplasts and thylakoids isolated from spinach were entrapped in six different polyvinylalcohol bearing styrylpyridinium groups (PVA-SbQ). Measurements of oxygen production were carried out in 0.01 M phosphate buffer (pH 6) at 25 °C. Immobilized preparations were compared for their electron transport activity measured as the initial rate of oxygen evolution with p-benzoquinone as artificial electron acceptor. The entrapped chloroplasts in PVA-SbQ 1700 and 3500 betaine retained 20% of their initial activity after 90-day storage in the dark at + 4 °C. A membrane made with PVA-SbQ 2300 kept 20% activity after 427-day storage at −18 °C in the dark whereas the same membrane retained only 10% activity after 90-day storage at + 4 °C in the dark. A 1% BSA concentration increased the stability of the membrane. The limits of detection (corresponding to a 10% inhibition) of atrazine were 10 μg/l and 12 μg/l for native and entrapped chloroplasts, respectively. The good stability of entrapped chloroplasts suggests that this system could be useful for the detection of pollutants in water.