Development of coupled redox active network in Ca-alginate polymer for immobilization of Pseudomonas putida 1046 on electrode surface

Highlights: • Ca-alginate polymer coated electrodes are fabricated. • The polymers are functionalized by developed coupled redox reaction network. • MTT formazan/phenazine methosulfate preserve redox activity within the polymer. • Current density of 35 ± 2 mA/m² has been achieved with functionalized bioanodes. -- Abstract: Redox activated polymeric gels on the anode surface present an approach for creating artificial biofilms thus ensuring highly effective extracellular electron transfer (EET) of electrogens in microbial fuel cells (MFCs). A new coupled redox reaction network was developed for functionalization of alginate polymerized on carbon felt and fast immobilization of bacteria. For this purpose, four different fabricated polymer-modified materials, consisting of single or mixed redox active dyes have been examined toward electrochemical activity and stability at abiotic as well as biotic conditions. The designed electrodes consisting of thiazolyl blue formazan/phenazine methosulfate (PMS) showed well-defined reduction and oxidation peaks with a formal potential of +91 mV (vs. SHE). The peaks' current exceeded two times those of PMS-alginate and over ten times those of thiazolyl blue formazan-alginate electrodes, while the alginate control did not express any activity. Selected redox polymer matrices on carbon felt supports were used for immobilization of bacteria Pseudomonas putida 1046. The modified bioanodes have been poised continuously at positive potentials +0.605 V and +0.705 V (vs. SHE) and current density of 35 ± 2 mA/m² has been achieved. The redox activity and charge transfer properties of the modified bioanodes were investigated by means of cyclic voltammetry and electrochemical impedance spectroscopy. The results in this study show that the non-conductivity of the alginate polymer can be overcome by the addition of artificial redox dyes thiazolyl blue formazan and PMS, creating a coupled redox network or by expression of cellular produced redox compound mediating the electron transfer though the polymer, so that the fabricated bioelectrodes can be applied as bioanodes in MFC.