Journal of Energy Bioscience 2024, Vol.15, No.2, 85-95 http://bioscipublisher.com/index.php/jeb 93 production and environmental protection. 9 Concluding Remarks The study of electron transfer mechanisms in electroactive bacteria within microbial fuel cells (MFCs) has revealed several critical insights. Extracellular electron transfer (EET) is a pivotal process in MFCs, enabling microbes to convert chemical energy from biomass into electrical energy. This process can occur via direct transfer through conductive pili or nanowires, or mediated transfer involving redox mediators such as flavins and pyocyanins. The efficiency of these mechanisms is influenced by the redox potentials of the species involved and the microbial oxidative metabolism. Research has highlighted the diversity of electroactive microorganisms, including iron-reducing bacteria like Geobacter sulfurreducens, which produce high power densities, and other microorganisms such as yeasts and hyperthermophilic archaea. The spatial structure of electroactive biofilms and the use of modified anodes, such as those incorporating iron phthalocyanine, have been shown to significantly enhance electron transfer and power density in MFCs. Additionally, mathematical models have been developed to predict the nanowire electron transfer mechanism, demonstrating that biofilm thickness has a minimal impact on MFC performance. The findings from these studies have several implications for the development of more efficient MFCs. Understanding the mechanisms of EET can lead to the optimization of microbial and electrode interactions, thereby enhancing the overall efficiency of MFCs. For instance, the use of electron-conducting polymers and the regulation of biofilm spatial structure can improve electron transfer rates and power output. Additionally, the strategic positioning of electrodes can optimize electrochemical performance and pollutant reduction, as demonstrated by the enhanced Cr(VI) reduction and bioelectricity production in MFCs with optimal electrode spacing. Furthermore, engineering strategies such as enhancing transmembrane electron transport, accelerating electron shuttle synthesis, and promoting microbe-electrode interface reactions can significantly improve the EET capabilities of electroactive microorganisms. The integration of advanced nanostructured materials, such as carbon nanotubes and graphene, has also been shown to enhance bidirectional EET processes, potentially expanding the practical applications of MFCs. The future of research on electroactive bacteria in MFCs is promising, with several avenues for further exploration. Continued investigation into the molecular aspects of EET mechanisms, particularly in less-studied microorganisms, will provide deeper insights into optimizing MFC performance. The application of systems biology and synthetic biology approaches can lead to the development of high-performance electroactive microbial systems, potentially revolutionizing bioelectrochemical technologies. Moreover, the use of redox mediators in microbial electrocatalysis offers opportunities to enhance charge transport and electrochemical reactions at the microorganism-electrode interface, promoting the widespread application of MFCs in various environmental and industrial processes. As research progresses, the integration of novel materials and engineering strategies will likely lead to more efficient and sustainable MFCs, contributing to the advancement of renewable energy technologies and environmental remediation efforts. In conclusion, the study of electron transfer mechanisms in electroactive bacteria within MFCs has provided valuable insights that can drive the development of more efficient and versatile bioelectrochemical systems. Continued interdisciplinary research and technological innovation will be key to unlocking the full potential of MFCs in the future. Acknowledgments I would like to express gratitude to the two anonymous peer reviewers. Conflict of Interest Disclosure
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