Heterologous Synthesis of Polyunsaturated Fatty Acids for Aquaculture

th The United States is a minor aquaculture producer ranking 17 in global aquaculture productionbut it is the leading importer of fish and fish products. Even though U.S. aquaculture has beengrowing at 12 to 14% per year we still depend heavily upon imports. By value 90% of theseafood we eat originates abroad. The USDA Aquaculture priorities are to identify and addressthe needs or constraints that limit U.S. aquaculture. These include "Improved production systemsand management strategies for efficiency and reduced environmental impacts." Xylome'sproposed research and development aims directly at this limitation by creating a novel pathwayto provide high omega-3 (w3) long-chain polyunsaturated fatty acids (LC-PUFAs) as a criticalcomponent of aquaculture feed. Currently the predominantway to obtain w3 for aquaculture isby harvesting wild fish stocks which are becoming rapidly depleted and more expensive torecover. In order for aquaculture to be sustainable a source of w3 that does not rely on wild fishstocks must be found.Although other emerging sources of omega-3 oils can be isolated fromalgae and GMO rapeseed these de novo crop sources are less efficient on a CO emission and2 cost basis than the inexpensive stillage-based fermentations being developed by Xylome.Wepropose to use byproducts from midwestern agriculture (predominantly C-4 corn) drawing onstillage byproducts from ethanol production and soy protein to create a fish-free high proteinhigh w3 fatty acid diet for intensively cultivated salmon and other species. Xylome hasdeveloped a novel highly lipogenic yeast strain capable of producing 85% of its dry weight inlipid. We intend to clone genes from marine Thraustochytrium sp. which natively make high w3fatty acids such as EPA and DHA into our lipogenic yeast and re-direct its metabolic activity toLC-PUFA synthesis. By using domestically produced soy protein and lipogenic yeast we will beable to establish a safe aquaculture feed that is not dependent on marine fisheries for high w3 fishoil. This will support food safety improve efficiency of aquaculture production through a rapidlyemerging inland salmon farm industry reduce the spread of diseases parasitic infections andescape of farmed fish into native ecosystems and it will help preserve marine ecosystems byproviding a fish-free feed. It will also improve water conservation and reduce carbon emissionsby recycling an agriculture waste byproduct.