Natural electron mediators induce current in micro photobiological fuel cells

One of the promising green energy solutions is the usage of microbiological fuel cells (MFCs). MFCs are composed of bacteria which produce electrical current by reducing the anode in bio electrochemical cells. Addition of external electron mediators such as ferricyanide, quinones or phenazines can assist in increasing the current. Although MFCs seem to be a cheap promising solution, their large-scale cultivation requires large amounts of sugar sources and may be considered as environmental pollution themselves. Photobiological fuel cells (PMFCs) use cyanobacteria or other photosynthetic systems. In addition to electron transport mechanisms that exist in bacteria, cyanobacteria can also produce electricity based on their photosynthetic pathway as electron source. Since they can produce glucose doing photosynthesis, they are cheaper to grow. They can also be found in nature in very high quantities in oceans and lakes.

Most of the PMFCs are based on the model species Synechocystis. This raised the question whether other cyanobacteria can be exploited? Addition of Ferricyanide as electron mediator managed to induce the photocurrent. However, it is toxic to the cells and decrease their viability.

In our work, we produced photocurrent from various cyanobacterial cells which grow in fresh and sea waters. We have also found that addition of the natural non – toxic electron mediators NAD⁺ and NADP⁺ increase the photocurrent in PMFCs. Quantification of this effect was done using screen printed electrodes.