Evaluation of a Yeast-Polypyrrole Biocomposite Used in Microbial Fuel Cells

Electrically conductive polymers are promising materials for charge transfer from living cells to the anodes of electrochemical biosensors and biofuel cells. The modification of living cells by polypyrrole (PPy) causes shortened cell lifespan, burdens the replication process, and diminishes renewability in the long term. In this paper, the viability and morphology non-modified, inactivated, and PPy-modified yeasts were evaluated. The results displayed a reduction in cell size, an incremental increase in roughness parameters, and the formation of small structural clusters of polymers on the yeast cells with the increase in the pyrrole concentration used for modification. Yeast modified with the lowest pyrrole concentration showed minimal change; thus, a microbial fuel cell (MFC) was designed using yeast modified by a solution containing 0.05 M pyrrole and compared with the characteristics of an MFC based on non-modified yeast. The maximal generated power of the modified system was 47.12 mW/m(2), which is 8.32 mW/m(2) higher than that of the system based on non-modified yeast. The open-circuit potentials of the non-modified and PPy-modified yeast-based cells were 335 mV and 390 mV, respectively. Even though applying a PPy layer to yeast increases the charge-transfer efficiency towards the electrode, the damage done to the cells due to modification with a higher concentration of PPy diminishes the amount of charge transferred, as the current density drops by 846 mu A/cm(2). This decrease suggests that modification by PPy may have a cytotoxic effect that greatly hinders the metabolic activity of yeast.

Automated summary

Electrically conductive polymers have potential applications in charge transfer from living cells to electrochemical biosensors and biofuel cells. Modification of living cells by polypyrrole (PPy) reduces cell lifespan, burdens replication, and diminishes renewability. The study evaluated the viability and morphology of non-modified, inactivated, and PPy-modified yeast cells, showing a reduction in cell size, increased roughness, and the formation of polymer clusters with higher pyrrole concentrations. A microbial fuel cell (MFC) designed with yeast modified by a 0.05 M pyrrole solution generated 8.32 mW/m(2) more power than the MFC based on non-modified yeast. However, higher concentrations of PPy caused cytotoxic effects and reduced charge transfer efficiency.