Redox-active molecules in bacterial cultivation media produce photocurrent

In recent years, global climate change has urged the importance of developing new clean energy technologies that may replace the combustion of fossil fuels and help to reduce carbon emissions. A promising, yet intrinsically complex solution, is the utilization of bacteria as electron donors in microbial fuel cells (MFCs). In this work, we show that just the cultivation media for bacterial growth, which is based on yeast extract, is sufficient for generating electrical current in a bio-electrochemical cell (BEC). We apply cyclic voltammetry and 2-dimensional fluorescence spectroscopy to identify redox active molecules such as NADH, NAD+, and flavines that may play key roles in electron donation. Finally, we show that upon illumination, current production is enhanced 2-fold. This photocurrent is generated by a variety of metabolites capable of photochemical reduction, enabling them to donate electrons at the anode of the BEC. Future investigations into the role of culture media versus that of living cells in MFCs may aid in reducing overall production and maintenance costs, and enhance power output performance. ### Competing Interest Statement The authors have declared no competing interest.