Figure 5. Recycling of the biocatalyst.

A 500 µl aliquot of magnetosomes suspension is immobilized onto the magnetic column. A 1 ml sample contaminated with 50 µM ethyl-paraoxon is passed through the column by flow gravity and recovered for p-nitrophenol spectrophotometric assay. The column is stored at room temperature with the magnetosomes and the experiment is repeated two more times at 2-hour intervals. Magnetosomes still magnetically retained on the column are stored at 4°C overnight and the entire set of experiments is repeated the next day. The hydrolysis activities are plotted for each repeat (100% activity expresses the complete degradation of ethyl-paraoxon by the purified enzyme) for day 1 (red) and day 2 (blue).