Metabolic engineering of Phaeodactylum tricornutum for the enhanced accumulation of omega-3 long chain polyunsaturated fatty acids

We have engineered the diatom Phaeodactylum tricornutum to accumulate the high value omega-3 long chain polyunsaturated fatty acid docosahexaenoic acid (DNA). This was achieved by the generation of transgenic strains in which the Delta 5-elongase from the picoalga Ostreococcus tauri was expressed to augment the endogenous fatty acid biosynthetic pathway. Expression of the heterologous elongase resulted in an eight-fold increase in docosahexaenoic acid content, representing a marked and valuable change in the fatty acid profile of this microalga. Importantly, DNA was shown to accumulate in triacylglycerols, with several novel triacylglycerol species being detected in the transgenic strains. In a second iteration, co-expression of an acyl-CoA-dependent Delta 6-desaturase with the Delta 5-elongase further increased DNA levels. Together, this demonstrates for the first time the potential of using iterative metabolic engineering to optimise omega-3 content in algae. (C) 2013 The Authors. Published by Elsevier Inc. On behalf of International Metabolic Engineering Society. All rights reserved