A synthetic biology approach to optimisation of microbial fuel cell electricity production

化石燃料储量的枯竭、全球变暖、能源安全以及对清洁、廉价燃料的需求，使开发可再生能源成为全球研究的重点。微生物燃料电池（mfc）有潜力从废水、农业副产品和工业污染物等大量碳源中产生可再生电力。在MFCs中，来自微生物代谢的电子从细菌流向阳极，然后通过外部电路，最终在阴极将氧转化为水，结束循环。mfc的优点是，根据所需的应用，它们可以从微流体到废水处理厂的规模变化。通过探索代谢碳源的范围，修改燃料电池的设计和电极组成，以及研究mfc中微生物群落组成和结构，已经发表了大量关于优化微生物燃料电池发电的工作。然而，在这项技术能够有效地投入使用之前，仍有许多障碍需要克服。MFC系统的优化是一个高度跨学科的研究领域，需要两个互补的工作领域：首先是通过传统工程设计更高效的细胞硬件，其次是通过生物工程了解和改善微生物与电极之间的相互作用和电子传递。在MFC发展中最重要的工程挑战之一是从细菌到阳极的有效电子转移。到目前为止，已经确定了三种将电子从细菌细胞转移到电极的可能方法-直接通过细胞表面细胞色素（例如希瓦氏菌），通过毛作为纳米线（例如地杆菌）或通过产生可溶性电子介质化合物（例如假单胞菌sp非那嗪的生产）。电池与阳极接触、电子转移以及MFC功能的基础是在电极表面形成专门的生物膜。研究表明，mfc的功率输出和功率密度直接取决于生物膜的生长和组成。本提案的目标是使用合成生物学方法来重组细菌，以可预测和有效地产生电子并将电子转移到微生物燃料电池电极，从而产生高度通用，可靠和可持续的能源。合成生物学旨在使用严格的工程方法来设计和构建新的标准化生物部件、设备和系统，或重新配置现有的部件、设备和系统以提高效率或执行新功能，并有可能彻底改变我们概念化和处理生物系统工程的方式。该项目旨在-a)创建一个生物部件和设备的合成生物学工具箱，以便于电致微生物菌株的工程设计和遗传电路的构建，以增强纳米线菌毛的生产，表面活性细胞色素和电子中介化合物的生产。b)使细胞具有增强的电子传递能力。c)研究由工程细菌单独形成的电极生物膜的结构和组成，以及它们相互结合形成的电极生物膜，以及它们在引入来自各种废水的天然阳极生物膜时的普遍性和持久性。d)细菌中碳代谢的多功能性将被设计成扩大利用污染物作为碳源进行发电代谢的范围和效率，关闭废物处理能源产生循环，这将对广泛的工业产生明显和巨大的好处。

The depletion of fossil fuel reserves, global warming, energy security and the need for clean, cheap fuels has made developing sources of renewable energy a global research priority. Microbial Fuel Cells (MFCs) have the potential to generate renewable electricity from a vast array of carbon sources such as waste-water, agricultural by-products and industrial pollutants. In MFCs electrons from microbial metabolism flow from the bacteria toward an anode then on through an external circuit finally converting oxygen into water at the cathode closing the cycle. MFCs have the advantage that they can vary from micro fluidic to waste water treatment plant scale depending on the desired application. A great deal of work has been published on optimizing microbial fuel cell electricity generation by exploring the range of carbon sources for metabolism, modifying the design and electrode composition of the fuel cell and examining the microbial community composition and structure occurring in MFCs. However there are still many obstacles that need to be overcome before this technology can be effectively put to use. The optimization of MFC systems is a highly multidisciplinary area of research and two complementary areas of work are required - firstly to design more efficient hardware for the cells by traditional engineering and secondly to understand and improve the interaction and electron transport between microbes and electrode via biological engineering. One of the most important engineering challenges in MFC development is the efficient electron transfer from the bacteria to the anode. To date three possible methods of transferring electrons from bacterial cells to the electrode have been identified - directly via cell surface cytochromes (e.g. Shewanella spp), via pili acting as nanowires (e.g. Geobacter spp) or via the production of soluble electron mediator compounds (e.g. Pseudomonas sp phenazine production). Fundamental to cell contact with the anode, electron transfer and thus the functioning of the MFC is the formation of specialized biofilms on the electrode surface. It has been shown that the power output of MFCs and that the power density was directly dependent on biofilm growth and composition. The objective of this proposal is to use a synthetic biology approach to reengineer bacteria to predictably and efficiently generate and transfer electrons to microbial fuel cell electrodes resulting in a highly versatile, reliable and sustainable energy sources. Synthetic biology aims to use a rigorous engineering approach to design and build new standardized biological parts, devices and systems or to reconfigure existing ones to be more efficient or to carry out new functions and has the potential to revolutionise how we conceptualise and approach the engineering of biological systems. This project aims to -a) Create a synthetic biology toolbox of biological parts and devices for the easy engineering of electrogenic microbial strains and the construction of genetic circuits for the enhanced production of nanowire pili, surface active cytochromes and production of electron mediator compounds. b) Engineer cells to have enhanced electron transfer capabilities. c) Investigate the structure and composition electrode biofilms formed by the engineered bacteria individually, in combination with each other and their prevalence and persistence when introduced to a naturally occurring anodic biofilm derived from a variety of waste-waters. d) The versatility of carbon metabolism in the bacteria will be engineered to expand the range and efficiency of utilising pollutants as carbon sources for electricity generating metabolism closing the waste disposal energy generation loop which would be of obvious and enormous benefit to a wide range of industries.