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Study of Electron Transfer Mechanism in Biofilms


Microbial fuel cell (MFC) is a major type of bioelectrochemically systems (BESs) that focus on the direct electricity production from biodegradable materials. Furthermore, applications have been developed through utilizing this electrical current to produce H2 (microbial electrolysis cells, MECs), or driving water desalination (microbial desalination cells, MDCs). However, one major challenge for widespread integration of MFCs or BESs is the low amount of electricity generated.

Instead of optimizing of the fuel cell design or scaling–up electrode area to enhance the output energy of MFCs, the key factor for improving the electricity production in MFCs is to understand the extracellular electron transfer (EET) mechanism, metabolic activities and metabolism of the microbes used in such MFCs and BESs.

Chapter 2 introduces dissimilatory metal-reducing bacteria, such as Shewanella oneidensis MR-1 and Geobacter spp harness energy from metabolism. We demonstrate an on-chip electrochemical system to study the EET pathway on both Shewanella oneidensis MR-1 and Geobacter spp under aerobic and anaerobic conditions.

Chapter 3-4 explores electron transfer from an electrochemically active bacteria (EAB) to an insoluble substrate such as Fe(III), Mn(IV) and U(VI) can occur by direct or mediated electron transfer pathway. However, it is critical to understand the EET mechanisms and metabolism of the microbes in biofilms which used in MFC.

By exploring the specific interaction between Shewanella oneidensis MR-1 and insoluble substrate, the remarkable chemical factor has been discovered to influence the recognition, motion attachment/detachment and colonization between Shewanella oneidensis MR-1 and Fe2O3 substrate. We also developed a method for studying the EET pathway, metabolic activities status and behavior of microbes for maximal current production in the microfluidic flow system. The dissimilatory metal-reducing bacteria (DMRB) Shewanella oneidensis MR-1 wild type (WT), mtrComcA and bfe mutant cells are the model organisms for in-situ real time electrochemical current measurement. Our goal is to develop a novel bioelectronic device to study the EET mechanism, bacteria behavior in single cell level, metabolic activities status, bacteria behavior for maximal electricity production without artificial modification or coloration process.

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