14-PSIL: Plug and Play Photosynthesis for RuBisCO Independent Fuels

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Solar energy is a sustainable resource exceeding predicted human energy demands by >3 orders of magnitude. If this diffuse solar energy can be concentrated and stored efficiently, then it has the capacity to provide for future human energy needs. The process of oxidative photosynthesis, namely the reduction of CO2 utilizing light and water by photoautotrophs, stores solar energy in reduced carbon compounds, which are useful fuels for society. Although oxidative photosynthesis evolved some 3.5 billion years ago, it remains inefficient at converting solar energy into chemical energy and, ultimately, biomass. Commercial photovoltaics in concert with electrolyzers split water to produce hydrogen at an efficiency of approximately 10%. Photosynthetic yields for plants in optimal conditions typically do not exceed 1%, and higher-yielding microalgae species are estimated to have 3% efficiency. Under most conditions, the biological transformation of light to stored chemical energy is not limited by light but by the rate of carbon reduction. The goal of this project is to engineer pathways for diverting photosynthetic energy from linear electron flow (LEF) to alternative sinks, thereby providing alternate routes for "excess" photosynthetic capacity when carbon fixation is saturated. Our strategy is to engineer an intercellular, plug-and-play platform (PNP) that allows us to move electrons and/or reduced chemicals from modified photosynthetic source cells to independently engineered fuel-production modules that bypass the inherently inefficientcarbon-fixing catalyst RuBisCO. The realization of this goal will require radical manipulation of the fundamental biology of photosynthesis and development of novel synthetic biological, chemical, and analytical techniques.