As the issue of energy shortage becomes more and more severe, alternative clean and renewable energy source is in urgent need for the sustainable development of global society. Fuel cells as a promising solution have primary drawback of high cost due to using noble catalyst such as Pt. Microbial fuel cell (MFC) greatly reduces the cost by using biocatalyst. Nevertheless, previous efforts focused on using microbial consortium as catalyst for electrode reactions of which the actual working bacteria species is not always isolated and identified. Meanwhile, the power generation efficiency as a result of electron transport activity of bacteria could not reach the magnitude of application unless the electron transport activity is understood for the actual working bacteria species. To...[ Read more ]

As the issue of energy shortage becomes more and more severe, alternative clean and renewable energy source is in urgent need for the sustainable development of global society. Fuel cells as a promising solution have primary drawback of high cost due to using noble catalyst such as Pt. Microbial fuel cell (MFC) greatly reduces the cost by using biocatalyst. Nevertheless, previous efforts focused on using microbial consortium as catalyst for electrode reactions of which the actual working bacteria species is not always isolated and identified. Meanwhile, the power generation efficiency as a result of electron transport activity of bacteria could not reach the magnitude of application unless the electron transport activity is understood for the actual working bacteria species. To this end, we are driven to use single pure strain to study the points that could lead to improvement of the performance of MFC. Three approaches were adopted in this thesis: 1) System design using single chamber configuration to substitute the traditional H-type design. The power output was significantly enhanced by reducing the internal resistance. 2) Novel pure strains, Pseudomonas putida sp. MnB1 and Rhodobacter capsulatus were found to be able to work as biocathode without any other added electron shuttles to accept electrons from the electrode. The power output could rise at least 3 times compared with the abiotic growth medium control. 3) Broaden the matching of bacteria and mediator. An artificial mediator Vitamin K₃ was used to facilitate electron transfer from Synechocystis sp. PCC 6714 in both autotrophic and heterotrophic condition. Unlike what was previously believed, no cytotoxicity of the mediators to the bacterial cells was observed. Hence, the toxicity is not responsible for the unsustainable performance. Instead, the current generation is limited by intracellular glycogen content which is excreted to the solution. To make full use of the excreted glucose, a self-fueling MFC was constructed by combination of Synechocystis sp. PCC 6714, Shewanella Oneidensis, with addition of VK₃ to achieve higher energy efficiency of the system.