Bilirubin oxidase-based cathode for microbial fuel cell (MFC) applications: The effects of bacterial/pollutants' presence on enzyme stability

The trends of open circuit potential (OCP), current density achieved at 0.25V and the polarization behavior of bilirubin oxidase (BOx) based cathode was examined over a period of 12 days. A single chamber was used as the half electrochemical cell. The electrolyte used was phosphate buffer solution (PBS, 100 mM) with or without the addition of activated sludge. The AS was used as bacterial/pollutants source to evaluate the enzymatic degradation due to bacterial contamination. The cathodes were poised at 0.3V for the first two days, 0.2V during the following two days, and 0.1V in the remaining time of the tests. At the beginning, the OCPs were slightly higher than 0.5 V for the PBS solution and the PBS/AS solution. Over time the OCPs decreased and after 12 days, the cathode facing PBS had an OCP of 0.415 V while the one in the PBS/AS solution had a low OCP (0.3 V), which was the typical OCP achieved by the material only without enzymes addition, underlining the probable complete deactivation/poisoning of the enzymes.