Autotrophic Production of Limonene in Engineered Microalgae Chlamydomonas reinhardtii
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Biosynthetic alternatives for high-density petroleum derived tactical fuels, like JP-8 and JP-10, remain elusive given their tremendously high energy densities, low temperature viscosity and cloud point. Limonene, a bicyclic terpene abundant in pine resin, may supplant non-renewable aromatic compounds used in current aviation-fuel mixtures. Tractable microbes, such as yeast and E. coli, can yield high titers of hydrocarbon, but at the expense of increasing sugar and carbon inputs required by heterotrophs. Here we report a metabolic engineering approach, wherein photosynthetic carbon-flux is rerouted towards limonene in the microalgae Chlamydomonas reinhardtii. Conceptually, determining baseline capability of monoterpene production in algae will pave the way for advanced autotrophic hydrocarbon production. The research thus aims to address the technical barrier of engineering an algae-based autotrophic production system to produce the bicyclic terpene D-limonene to serve as a renewable jet fuel. The broader implication of limonene detected in the headspace of closed photobioreactors is significant on two accounts: First, limonene is emitted from microalgae and volatilized into the airspace above the liquid culture – key for future bioseperations approaches harvesting limonene; and second, redirecting photosynthetic carbon-flux away from crucial sterols/carotenoids/pigments towards volatile limonene will not negatively impact overall biological function and cell viability.
Syrenne, Ryan Douglas (2016). Autotrophic Production of Limonene in Engineered Microalgae Chlamydomonas reinhardtii. Master's thesis, Texas A & M University. Available electronically from