A Novel Oil Secretion Mechanism for Cost-Effective Algal Biofuel Production

There is an urgent need for domestic sources of low-cost, large-scale renewable biofuels. Micro-algae are one of most promising sources of renewable energy, with high potential per-acre oil productivity, minimal competition with arable land and limited freshwater supplies, and efficient recycling of CO2 emissions, as summarized in the D.O.E. & apos;s 2010 National Algae Biofuel Roadmap. However, current production costs are prohibitively high. Using our exclusive nuclear gene expression algae platform, we are engineering genetic systems to make cells secrete the oils they synthesize. Secretion turns cells into microscopic oil-producing factories, eliminating harvesting and oil extraction steps in conventional algal oil production, thereby channeling a much larger fraction ( & gt;90%) of captured sun energy and fixed carbon dioxide into oil. Our unique secretion solutions are engineered to actively secrete oils trapped in lipid droplets, in which the hydrophobic reduced-carbon compounds are compartmentalized and thus are not toxic to the cells. This contrasts with secretion strategies, pursued by other companies, that engineer cells to make cell-permeable fuels or fuel precursors (hydrocarbons or fatty acids). These compounds are solvents or detergents that are toxic, limiting yields. Our strategy is to modify naturally existing processes used by cells to secrete non-oil payloads (e.g., proteins or virus particles) to instead secrete intracellular oil droplets. We will do this by engineering proteins that contain a protein fragment that binds lipid droplets fused to a protein fragment that normally secreted by the cell. We will then express these candidate fusion proteins in our algae platform and look for lipid droplet relocalization from their normal locations, and/or secretion of lipid droplets. We will then complete the Phase I feasibility analysis by initial modifications to the fusion proteins (protein engineering) and to the cells (metabolic and cellular engineering by RNAi gene knockdowns or incorporation of other beneficial mutations). If this work is successful, we will a) prove the feasibility of our secretion strategy, and b) map a path for further optimization and scale-up to pilot scale in Phase II. Our long-term objective is to coordinately develop the biological solutions and production process to commercial production scales. If this work is carried into Phase II and beyond, this work will help to enable low-cost, large-scale production of domestic renewable fuels and begin realizing their enormous potential environmental, economic, and national security benefits.