Tuesday, November 10, 2009 - 10:00 AM
Production of Omega-3 Fatty Acids by Fermentation of Engineered Yeast
Dongming Xie, David Short, Quinn Zhu, Zhixiong Xue, Narendra Yadav, Pamela Sharpe, Raymond Hong, J Martin Odom, Shu-Chien Liang, Bjorn Tyreus, and Ethel Jackson. Central Research & Development/ Biochemical Sciences & Engineering, DuPont, Experimental Station, Rt. 141 and Henry Clay, Wilmington, DE 19880
The omega-3 fatty acids, cis-5, 8,11,14,17-eicosapentaenoic acid (C20:5; EPA) and cis-4,7,10,13,16,19-docosahexaenoic acid (C22:6; DHA), have been shown to confer wide-ranging health benefits against e.g., cardiovascular disease, rheumatoid arthritis, Alzheimers disease, lung fibrosis and inflammatory bowel disease. Unfortunately, humans do not synthesize omega-3 fatty acids in the amounts necessary to derive their health benefits and must obtain them in our diet. Currently, the major sources for omega-3 fatty acids are fish oil, microalgae, and a limited number of species of plants. Due to high costs, uncertain availability, deficiency of specific nutrients, and many other disadvantages within the current sources, DuPont has developed a clean and sustainable alternative source of omega-3 fatty acids through fermentation using a metabolically engineered strain of Yarrowia lipolytica. Specifically, desaturase and elongase genes have been introduced into the oleaginous yeast to utilize certain carbon sources to synthesize omega-3 fatty acids under fermentation conditions. The strain candidates were evaluated via culture tubes, shake flasks, and fermentor experiments. The typical fermentation process consists of a nitrogen-rich growth phase and a nitrogen-starved oleaginous phase. Medium components (e.g., nitrogen source) and process conditions (e.g., pH control, base addition) were optimized to improve the omega-3 fatty acid production. Mathematical modeling was a useful tool to analyze, optimize, control, and scale-up the fermentation process. The genetically engineered yeast produced more than 55% EPA in the accumulated oil under the optimized conditions (corresponding to the highest omega-3 fatty acid reported so far in the oil), and thus building a solid base for future commercialization.