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A Single Diatom Accumulates EPA and DHA High Value Omega-3

15 January 2014

UK - Rothamsted Research scientists have demonstrated for the first time the use of metabolic engineering in microalgae to modify the accumulation of high value Omega-3 fatty acids.

Marine microalgae and diatoms are the primary producers of eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) long chain polyunsaturated fatty acids (LC-PUFAs) in the aquatic food web.

As Omega-3 LC-PUFAs have been shown to be important for human health and nutrition there is an increasing demand for these high value fatty acids. Marine microalgae cultivation is one of the sources of these oils.

Currently no single algal strain accumulates high concentration of EPA and DHA. The diatom Phaeodactylum tricornutum naturally accumulates high levels of EPA and is considered a good source for its industrial production. However, it accumulates only trace of DHA.

Rothamsted Research scientists, funded by the BBSRC, have used metabolic and genetic engineering and demonstrate for the first time that it is possible to achieve an eight-fold increase in DHA content in P. tricornutum. The study is published in the journal Metabolic Engineering.

EPA and DHA are the Omega-3 LC-PUFAs that are beneficial for health. They modulate both metabolic and immune processes and confer the health benefits in areas of Cardiovascular Heart Disease (CHD) and neurodevelopment.

Plant sources of Omega-3, e.g. Flax seed, do not produce EPA and DHA; instead they produce shorter chain Omega-3 fatty acids such as a-linolenic acid (ALA). ALA does not confer the health-beneficial properties associated with EPA and DHA, despite the former also being an Omega-3 fatty acid.

The primary source for Omega-3 EPA and DHA are marine algae and diatoms and other photosynthetic organisms that comprise the phytoplankton. Microalgae and diatoms are consumed by fish, which then accumulate these oils. The increasing demand for fish oils puts pressure on the natural marine resources and highlights the need to identify alternative sustainable sources of Omega-3 LC-PUFAs. At Rothamsted Research scientists strategically supported by the BBSRC are using metabolic and genetic engineering towards developing sustainable alternative sources of EPA and DHA.

Dr Olga Sayanova, Rothamsted Research leading the present study said: “We are delighted to have been able to use two genes from the picoalga Ostreococcus tauri in the diatom P. triconutum and successfully alter the Omega-3 content in the latter. Successful expression of more than on egeens in a diatom has never been shown before. We have developed over the years, excellent molecular biology tools that now enable us to achieve such genetic modifications. In the current study we managed to develop a strain of the diatom that can now accumulate both EPA and DHA. Naturally the diatom produces ~35 per cent EPA and only traces of its total oil content. The transgenic diatom strain that we developed can convert a substantial portion of the EPA that they make to DHA. Therefore we have successfully generated the first transgenic diatom that can synthesise both of these high value omega-3 LC-PUFAs.”

Professor Johnathan Napier of Rothamsted Research who is leading the Metabolic Engineering research group and is supported by the BBSRC said: “The need for alternative sources of omega-3 LC-PUFAs becomes increasingly more pressing and we ought to investigate all possible alternative sources. We are very excited with the results of the current study, as it will significantly contribute to the establishment of the diatom P. tricornutum as an algal synthetic biology framework for the production of high value oils.”

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