Electrochemical analysis of extracellular electron transfer process of Pseudomonas aeruginosa NEJ07R using pyocyanin on a carbon electrode

Abstract

Indirect extracellular electron transfer (IEET), or mediated electron transfer (MET), is a process that has attracted attention for its application in electrochemical-microbial technologies for power generation, wastewater treatment, or electrofermentation. Pseudomonas aeruginosa is a bacterium known to carry out IEET because it produces its own redox mediator (RM), pyocyanin (PYO), which has electrochemical properties such as a high electron transfers rate and low resistance to charge transfer. However, other physical processes, such as PYO adsorption on the electrode, can alter that function. In this work, interaction parameters and adsorption-free energy values were determined to obtain an adsorption mechanism on a carbon-based electrode. Furthermore, the effect of PYO addition and its adsorption were studied in the IEET process of P. aeruginosa NEJ07R. The electrochemical profiling of PYO by cyclic voltammetry (CV) and chronocoulometry (CC) measurements allowed the calculation of the Laviron interaction parameter (ν'gθT). Since the values of ν'gθT > 0, it was determined that PYO maintains attractive interactions with the surface in cathodic and anodic reaction. Moreover, the low interaction free energies (ΔG0' ≈ −2.91 ×10−5 ± 1.28 ×10−8 kJ/cm3 and -−2.92 ×10−5 ± 2.74 ×10−8 kJ/cm3 for reduction and oxidation, respectively) suggests that the interactions are weak. As for the IEET of P. aeruginosa NEJ07R, the microbial catalysis process on a carbon cloth electrode was confirmed by adding PYO to the electrochemical cell. Electrochemical and FT-IR characterization confirmed the adsorption of PYO on the surface, so it is proposed that P. aeruginosa NEJ07R takes advantage of PYO adsorption to carry out IEET.