Bacterial sensors based on Acidithiobacillus ferrooxidans

An amperometric bacterial sensor with current response to Fe 2+ and S 2 O 3 2− ions has been designed by immobilizing an acidophilic biomass of Acidithiobacillus ferrooxidans on a multi disk flat-front oxygen probe. The bacterial layer was located between the oxygen probe and a membrane of cellulose. A filtration technique was used to yield the bacterial membranes having reproducible activity. The decrease of O 2 flow across the bacterial layer is proportional to the concentration of the dosed species. The dynamic range appeared to be linear for the Fe 2+ ions up to 2.5 mmol L −1 with a detection limit of 9 × 10 −7 mol L −1 and a sensitivity of 0.25 A L mol −1 . The response of the biosensor is 84 s for a determination of 2 × 10 −4 mol L −1 Fe 2+ . Optimizing the Fe 2+ determination by A. ferrooxidans sensor was carried out owing to Design of Experiments (DOE) methodology and empirical modelling. The optimal response was thus obtained for a pH of 3.4, at 35 °C under 290 rpm solution stirring. S 2 O 3 2− concentration was determined at pH 4.7, so avoiding its decomposition. The concentration range was linear up to 0.6 mmol L −1 . Sensitivity was 0.20 A L mol −1 with a response time of 207 s for a 2 × 10 −4 mol L −1 S 2 O 3 2− concentration.