While solar bioenergy is potentially an abundant and environmentally benign energy source, natural photosynthesis is relatively inefficient owing to slow steps in the conversion of carbon dioxide into biomass. This project seeks to increase energy capture by photosynthesis by diverting energy away from the normal slow steps to potentially more efficient processes. The first major goal of the project is to demonstrate that energy, in the form of electrical current produced by photosynthetic organisms, can be transmitted from a photosynthetic, energy capturing cell to an energy-storing "factory cell" via biological nanowires (biowires). The second major goal of the proposed work is to show that the factory cell can be engineered to use energy to produce useful fuel compounds.
Broader Impacts: This project will create the foundation for new directions in bioenergy research, with potential for dramatic increases in the efficiency of solar energy capture and storage, while training the next generation of scientists and engineers needed to compete in emerging areas of bioenergy and biotechnology. The project will demonstrate that energy can be transferred directly between cells as bio-electricity. Furthermore, the biowire to be developed will serve as a future generic connector for electrically connecting distinct cell types to create novel, functional biofilms. The photosynthetic components constructed in this project will serve as prototypes to establish a new design paradigm. In addition to these benefits, the project will 1) provide valuable resources to catalyze other important research projects, 2) train undergraduate and graduate students and postdoctoral fellows in areas of technology relevant to critical national needs, 3) establish productive international collaborations, and 4) disseminate information relevant to basic and applied research and development in energy and biotechnology.
Solar energy is a sustainable resource exceeding human energy demands by >3 orders of magnitude. If this diffuse energy can be concentrated and stored, it has the capacity to provide for human energy needs. The biological transformation of light to chemical energy (photosynthesis) is limited by the rate of carbon reduction. The goal of this project has been to engineer pathways for diverting energy from carbon reduction to alternative sinks. Our strategy has been to engineer an intercellular, plug-and-play platform that allows electrons and/or reduced chemicals to move from photosynthetic cells to engineered fuel production modules, bypassing the inefficient carbon-fixing catalyst RuBisCO, thus increasing flux through natural electron dissipation pathways, creating electrical connections between cell types, and employing a soluble redox shuttle to transfer reducing equivalents between cells. This international and interdisciplinary project is building bridges between the US and UK scientific communities in critical areas of synthetic biology, photosynthesis, electrochemistry, catalysis, and metabolic regulation. The project represents a radical approach to surpass natural photosynthesis by engineering a modular division of labor through electrical and chemical connectivity. The aims are devised to generate transformative research for technological applications and enable the discovery of fundamental science. Our goal, therefore, is to establish a platform to open a vast new frontier to develop new modular photosynthetic technologies. The major aim outcomes of the project were to establish a novel system to study alternative photosynthetic electron transfer pathways and the characterization of interactions between exotic electron carriers and native photosystem I; 2) provided new insights of the interactions of low potential electron carriers and O2; 3) constructes a new model system for understanding macroscopic electron transfer in single crystals of cytochromes and in biological hydrogels that may serve as a test for mechanism of bionanowire mechanisms; 4) expressed for the first time exotic cytochromes in cytoplasm to allow for alternative electron transfer to occur in vivo; 5) discovered that exotic cytochromes can perform poorly not because they lack interactions with photosystem I, but because this interaction is too strong