Polyvinyl alcohol (P) was cross-linked with sulfosuccinic acid (S) to fabricate a proton exchange membrane for microbial fuel cell (MFC) applications. To minimize swelling the membrane was further cross-linked with tetraethyl orthosilicate, (T). A PST formulation selected which gave comparable dry ionic conductivity to Nafion was selected. The MFC assembly also contained graphite as the electrode with yeast (YMC) as the electron source and glucose as the carbon source. It was observed that the power and current densities were always greater when the yeast paste coated onto the graphite electrode was irradiated by the red light of a specific fluence. To investigate this observation more closely, cytochrome c from the equine heart is used as a control redox source with or without iron potassium ferrocyanide as a mobile charge carrier [Fe(CN<sub>6</sub>)<sup>3-</sup>]. The power curves were obtained for yeast, cytochrome c MEAs under darkness, red or blue light exposure were compared with similar power profiles with cytochrome c as the electron source. Here the protein was reduced, oxidized, pasted onto the electrode with or without the charge carrier. The power densities and protein form monitored using spectroscopy of the dissembled MEA using the absorption peak for oxidized (528 nm) and reduced (550 nm) forms of cytochrome c. The results show that the source of electron flow is in the mitochondria and that light promotes a reduced state, which enables greater electron flux and higher power densities to be obtained. Conversely, higher light fluence promotes the oxidized form and lowers the power densities.

Understanding electron flow in microbial fuel cell using isolated cytochrome c to simulate electron transfer chain using red or blue light stimulation

ACS Fall 2021

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