Heterologous Synthesis of Polyunsaturated Fatty Acids for Aquaculture

Heterologous Synthesis of Polyunsaturated Fatty Acids for AquacultureUSDA SBIR Phase II Applicationth The United States is a minor aquaculture producer ranking 18 in global aquaculture productionin 2022 but it is the leading importer of fish and fish products. Even though U.S. aquaculture hasbeen estimated to be growing at a compound annual rate of 4.1% we still depend heavily uponimports. By value 90% of the seafood we eat originates abroad and more than half of importedseafood is produced by foreign aquaculture. The USDA Aquaculture priorities are to identify andaddress the needs or constraints that limit U.S. aquaculture. These include "Improved productionsystems and management strategies for efficiency and reduced environmental impacts." Xylome'sproposed research and development aims directly at this limitation by creating a novel pathway toprovide high w3 long-chain polyunsaturated fatty acids (LC-PUFAs) as a critical component ofaquaculture feed. Currently the only way to obtain w3 for aquaculture is by harvesting wild fishstocks which are becoming rapidly depleted and more expensive to harvest. In order foraquaculture to be sustainable a source of w3 that does not rely on wild fish stocks must be found.We propose to use byproducts from midwestern agriculture drawing on stillage byproducts fromethanol production and soy protein to create a fish-free high protein high w3 fatty acid diet forintensively cultivated salmon and other species. Xylome has developed a novel highly lipogenicyeast strain capable of producing 85% of its dry weight in lipid. We have synthesized fivepolynucleotides based on genes found in the marine Thraustochytrium sp. which natively makeshigh w3 fatty acids such as EPA and DHA and we have introduced them into the genome of ourlipogenic yeast to re-direct its metabolic activity to LC-PUFA synthesis. By using domesticallyproduced soy protein and lipogenic yeast we will be able to establish a safe aquaculture feed thatis not dependent on marine fisheries for high w3 fish oil. This will support food safety improveaquaculture production efficiency reduce the spread of diseases parasitic infections and escapeof farmed fish into native ecosystems and it will help preserve marine ecosystems by providing afish-free feed. It will also improve water conservation and reduce carbon emissions by recyclingan agriculture waste byproduct.