On the Production of High-Purity Docosahexaenoic Acid from Heterotrophic Microalgae

Omega-3 fatty acids provide significant health benefits and are a popular nutritional supplement in the nutraceuticals industry. Omega-3 fatty acids such as docosahexaenoic Acid (DHA) and eicosapentaenoic Acid (EPA) have been reported to improve heart health and mental health. In addition, DHA consumption has been tied to improvements in infant cognitive development. Therefore, high-purity DHA is a desired ingredient in the production of infant formula. The omega-3 oils originating from fish tend to have carcinogenic risks in addition to a bad odor. In recent years, the industry trend has shifted to producing these omega-3 fatty acids via microalgae species– making it a profitable time to enter the DHA production market. The proposed design is for a plant to cultivate the Schizochytrium cells in the upstream process, and then extract and purify the desired omega-3 fatty acid oils in the downstream process. The project proposal called for production of 881,800 lb DHA per year, but our plant has the capacity to produce 1,148,000 lb DHA per year at a competitive price of $362.90 per lb of DHA. Clinton, Iowa was chosen as the plant location due to its proximity to the Mississippi River and the Archer Daniels Midland (ADM) plant, allowing for direct access to water and waste disposal. Our process is estimated to have an IRR of 153.8% with a NPV of $775,600,000 and a ROI of 206.5%. The process itself begins with fermentation of the microalgae cells, starting with lab-scale fermentors, increasing in size to seed fermentors, and finally scaling up to production fermentor size. Schizochytrium sp. is the strain of heterotrophic microalgae, chosen for its ability to accumulate lipids in high concentration, and its ability to produce DHA triglyceride in high selectivity with respect to other omega-3 fatty acids. Following fermentation, extraction operations are carried out with a hexane solvent and bead mill to extract the crude oils. The hexane is then evaporated and recycled back to the bead mill. The purification process of the crude oil involves saponification of the triglycerides into fatty acid salts. Acetic acid is then added to convert the salts into the final docosahexaenoic acid product. The saponification and protonation reactions take place in Scheibel columns. The final DHA product is 98% pure by mass, and will be sent to a pack out station to be packaged into pharmaceutical grade drums for customers. Disciplines Biochemical and Biomolecular Engineering | Chemical Engineering | Engineering This working paper is available at ScholarlyCommons: http://repository.upenn. edu/cbe_sdr/91 University of Pennsylvania Department of Chemical and Biomolecular Engineering 220 South 33rd Street Philadelphia, PA 19104 April 18, 2017 Dear Prof. Patel, Prof. Seider, and Prof. Vrana, Herein contains the solution to the design problem presented by Dr. Richard Bockrath. The proposed process design is for the industrial production of omega-3 fatty acids from the heterotrophic microalgae Schizochytrium sp. S31. The microalgae undergo aerobic fermentation in fermentors, which are successively scaled-up to production fermentor volumes. After twenty hours within the production fermentors, the nitrogen source is completely depleted. The Schizochytrium shift to a metabolic pathway that induces lipid accumulation. After lipid production, the cells are transferred to the downstream processes of extraction and purification. For extraction, water is removed and hexane is added. The hexane-biomass slurry runs through a bead mill to extract the crude oils from the biomass. A flash evaporator and wiped film evaporator system are used to evaporate the hexane and recycle it back into the bead mill process. The crude oil runs through two Scheibel columns, converting the triglyceride to the fatty acid product. Finally, the high-purity DHA will be filtered through a lamella filter to remove residual moisture. Antioxidants will be introduced for product stability, and the DHA will be packaged into pharmaceutical-grade drums for shipment. This report contains the detailed process design, economic analysis, conclusions, and recommendations for the implementation of the plant. The proposed plant is found to not only be economically feasible but also quite profitable. The calculated internal rate of return (IRR) is found to be 153.8%, and the net present value is found to be $775,600,000. At the price of $362.80 per pound of DHA, we anticipate a 206.5% return on investment (ROI) by its third year of production. Thank you for all the assistance provided to us during this project.