(421ba) Bioengineering a System for the Direct Production of Biological Hydrocarbons for Biofuels

Long-chain hydrocarbons, consisting of alkanes and alkenes, are the major constituents of the petroleum-based gasoline and diesel fuels that are in use today. Many types of organisms synthesize such hydrocarbons in nature, as epicuticular waxes and pheromones in insects, protective coatings on fungal spores, epicuticular waxes in higher plants, and for various purposes in many microorganisms, including blue-green and green algae, cyanobacteria, and yeasts, among others. But for all their ubiquity, the biochemical and genetic bases for how these compounds are synthesized are not well understood. Several biochemical mechanisms have been proposed for linear hydrocarbon biosynthesis, most notably the head-to-head condensation and elongation-decarbonylation pathways from fatty acid precursors, but definitive characterization of these and other possible mechanisms have largely remained elusive. Our project seeks to develop a biological system capable of generating a renewable source of linear hydrocarbons that are replacements for petroleum-based fuels. To achieve this vision, the biochemical and genetic bases for the biosynthesis of hydrocarbons must be identified, characterized, and engineered to produce fuel-ready hydrocarbons proficiently and economically. We have established three systems as models for biological hydrocarbon synthesis, including the freshwater algae Botryrococcus braunii, the marine algae Emiliania huxleyi, and the plant Zea mays. This project will identify the mechanism by which biological systems generate simple hydrocarbons such as n-alkanes and n-alkenes, and isolate their genetic and biocatalytic elements. These isolated genes will then be used to establish the vision of developing the biocatalytic-technology for the generation of a second-generation biofuel based on biologically derived hydrocarbons.