Bio-electrocatalysis of Acetobacter aceti through direct electron transfer using a template deposited nickel anode

Abstract

We have developed a novel anode for microbial fuel cells (MFC) which exhibits effective direct electron transfer with Acetobacter aceti. A high surface area nickel electrode was obtained using a simple process of template electrodeposition and it significantly improved the bioelectrocatalytic activity of Acetobacter aceti towards the oxidation of ethanol and glucose. Electrodeposition of Ni on carbon paper was carried out in the absence and presence of a soft template which served as the substrate for direct electron transfer. The soft template consists of a two component mixture of Triton X-100 and water. The structural and morphological characterizations of these modified electrodes were carried out using scanning electron microscopy (SEM). The redox properties of the biofilm formed on Ni coated carbon electrodes were investigated using cyclic voltammetry (CV) and chronoamperometry (CA). The formation of redox peaks during CV studies suggests the presence of a membrane bound redox protein linked to pyrroloquinoline quinone (PQQ) within these microbes on the modified electrodes. Investigation of the scan rate dependence reveals that the proteins are surface confined and anchored. From CA studies, we found that the oxidation current density corresponding to glucose and ethanol was more for the template deposited nickel (TNiCP) when compared to the one without the template. The oxidation current density of ethanol was found to be higher (68 μA cm⁻²i.e., 680 mA m⁻²) in comparison to glucose (42 μA cm⁻²i.e., 420 mA m⁻²). For comparison, we have also carried out all these studies using a bare carbon paper (CP). Our results clearly demonstrate the direct electron transfer between Acetobacter aceti and high surface area nickel electrodes through the membrane bound redox enzyme which presumably contributes to the higher oxidation current density of ethanol and glucose and could be used as an alternative anode material for MFC applications.