Development of a Phaeodactylum tricornutum biorefinery to sustainably produce omega-3 fatty acids and protein

Phaeodactylum tricornutum is a genetically well-studied microalga but commercial production of omega-3 fatty acids and protein had not been established. Here, a biorefinery platform to cost-effectively culture, harvest and process this diatom has been developed. Using a sea salt substitute supplemented with magnesium enabled low-cost land-based cultivation, reaching biomass yields of 0.17 g L−1day−1 and 340 g m−2day−1 in free-standing outdoor photobioreactors. pH-induced auto-flocculation in bioreactors or open ponds followed by solar drying was most cost-effective to harvest dry biomass. Lipids extracted by organic solvents accounted for 27.3% per dry biomass. Ethanol was the safest and most suitable option for a biorefinery yielding 92% of extractable omega-3 eicosapentaenoic acid (EPA) and 40.9% of protein in the defatted biomass. Using Central Composite Design, optimized alkaline extraction recovered 60.4% of total protein. A cost comparison to Nannochloropsis microalgae showed that EPA-rich oil and protein for human consumption are the most viable products with potentially lower EPA production costs. This study demonstrates that land-based P. tricornutum cultivation can provide a sustainable source of omega-3 fatty acid without putting pressures on marine bioresources.