Bioanodes

A construction of a biofuel cell is schematically illustrated in Fig. 23. A carbon felt sheet was used for both anode El and cathode E2. An anion-exchange membrane 180 /am thick was used for a separator membrane S. The contact area of S with the electrolyte in each compartment was 12.5 cm. Each compartment had an electrolyte solution (adjusted to pH 7.0 with NaH2P04 and Na2HP04) of 5 mL. The cell was used as a prototype biofuel cell to evaluate the performance of the fuel cell composed of a biocathode (ABTS / ABTS -B0D-02/H20) and a bioanode (MV /MV -Z). vulgaris (H)-2H /H2). The biofuel cell was operated with O2 and H2 gas bubbling in the cathode and anode compart-... 

As the cell membrane of microorganisms is non-conductive, how to transfer the electrons across the cell membrane (usually termed as extracellular electron transfer (EET)) is the key issue for MES. Eor the bioanode, extracellular electron transfer usually refers to outwards electron transfer, which is related to transportation of intracellular electrons to the solid electrode. To date, at least three electron transfer pathways have been explored, i.e., electron shuttle mediated electron transfer, outer membrane redox proteins mediated contact-based electron transfer, and conductive pili mediated electron transfer (Figure 5.5). ... 

Microfluidic Fuel Cells, Fig. 6 A complete microfluidic biofuel ceil featuring an upstream biocathode and a downstream bioanode integrated in a single microchannel. Magnifled views of the electrode dimensions (A ) and simulated oxygen concentration (A") in the chaimel are also provided (Reproduced with permission from Togo et al. [9]. Copyright Elsevier (2008))... 

The power of biofuel cells is directly related to the difference between the respective redox potentials of the electroenzymatic reactions occurring at each of the two electrodes the bioanode for glucose oxidation and the biocathode for the reduction of oxygen. The cell voltage and hence the power thus depends on the mode of enzyme wiring and therefore, the direct electron transfer is the most... 

Graphene nanoplatelets showed DET at both, bioanodes and cathodes using GOX and laccase, respectively. These connected bioelectrodes provided a maximum power output of 60 pW cm and 0.6 V OCP [28]. 

In bioanodes, an (in)organic electron donor is oxidized by microorganisms with concomitant liberation of electrons and protons (Figure 6.1). The electrons produced are shuttled through the internal electron transport chain of the microorganisms and are deposited on the anode. The energy level of the electrons deposited on the electrode is dependent on the terminal electron transfer molecule. 

Whereas numerous studies have reported on microbial-assisted electron transfer towards electrodes (bioanodes), only limited information is available on the reverse process. Bspecially the microbial electron uptake from cathodes by microorganisms needs thorough investigation. 

Second, biofllm thickness, structure, composition, and density affect the flux of substrates and products within the biofllm. The latter can result in large overpotentials, which have a negative impact on the performance of the system. In the case of bioanodes, higher power production was observed from thicker anodic biofilms [120]. Strikingly, the reverse effect has been observed in cathodic biofilms [35]. 

Andersen SJ, Pikaar I, Freguia S, Lovell BC, Rabaey K, Rozendal RA. Dynamically adaptive control system for bioanodes in serially stacked bioelectrochemical systems. Environ Sci Technol 2013 47 5488-5494. 

Piseiotta JM, Zaybak Z, Call DF, Nam J Y, Logan BE. Enrichment of microbial electrolysis ceU biocathodes from sediment microbial fuel cell bioanodes. Appl Environ Microbiol 2012 78(15) 5212-5219. 

---