High-Power Low-Cost Tissue-Based Biofuel Cell

We demonstrate the first example of using plant tissues for the operation of biofuel cells (BFC). A banana tissue rich with polyphenol oxidase (PPO), an enzyme able to reduce oxygen to water, was mixed with a carbon paste (banana/CP). The resulting tissue electrode was employed as the biocathode of a glucose biofuel cell based on a glucose dehydrogenase (GDH) bioanode. On the bioanode, multiwall carbon nanotubes (MWCNTs) are used as supports for the glucose-dehydrogenase (GDH) biocatalyst and the Meldola's blue (MDB) mediator, while the phenolic constituents of the banana serve as mediator for PPO. The maximum power output and open circuit voltage (OCV) of the banana-based tissue biofuel cell were 57 mu W/cm2 and 0.46V, respectively. Control experiments using the corresponding pure enzyme tyrosinase (Tyr) for the biocathode resulted in a substantially lower power output. Cost analysis of this tissue biofuel cell system indicates dramatic improvements in terms of the power-output/dollar compared to the common use of isolated enzymes (166502 mu W/$ vs. 17.8 mu W/$, i.e., 9354 times improvement). The banana-based biofuel cell displayed an extended lifetime of over 2 weeks with proper storage between experiments. We also demonstrate a fuel-free full plant-tissue based BFC concept, combining the banana biocathode with a bioanode based on germinated tomato-seeds that contain alcohol dehydrogenase (ADH), NAD+ and ethanol. Our findings indicate the potential of using plant tissues for the successful operation of efficient and cost-effective BFC.