Bacteria derived bioactive compounds: A valuable tool for the electrochemical detection of arsenic (III) ions in contaminated water

A simple, fast and cost-effective electrochemical approach is here reported for the selective and quantitative detection of arsenic (III) ions in water starting from bacteria derived bioactive compounds. The exopolysaccharide (EPS B3–15) produced by the thermophilic, heavy metal tolerant Bacillus licheniformis B3–15, and the biosurfactant obtained from Bacillus horneckiae SBP3 (BS- SBP3) were used as sensitive elements for the electrochemical detection of As³⁺ due to their known recognition abilities towards this toxic ion, their thermophilic properties and stability in harsh conditions. The covalent functionalization of screen-printed gold electrodes (SPGE) with these bioactive compounds demonstrated to be advantageous to selectively detect As³⁺ in contaminated waters. Electrochemical measurements, performed for the developed sensors SPGE-EPS-B3–15 and SPGE-BS- SBP3, at the normal range of pH in surface water systems (6.5–8.5) demonstrated a higher sensitivity towards As³⁺ with respect to the bare electrode, also in the presence of other competing ions, such as Al³⁺, Bi³⁺, Ni²⁺ and Pb²⁺,with very low limits of detection (0.19 nM for SPGE-EPS-B3–15 and 0.03 nM for SPGE-BS- SBP3), which are below the legal limits for these heavy metal ions in drinking water (10 μg/L). The reported sensitivity was 1.8 µA nM⁻¹cm⁻² for SPGE-EPS-B3–15 and 17.5 µA nM⁻¹cm⁻² for SPGE-BS- SBP3. The preferred detection abilities of the chosen bioactive compounds towards As³⁺ ions have been also confirmed by complete conformational analysis, using a combination of Molecular Dynamics (MD) and Density Functional Theory (DFT) studies.