Biosynthesis of Polyunsaturated Fatty Acids in Marine Protists

Marine protists synthesise long-chain polyunsaturated fatty acids (PUFAs), notably eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), through two principal biosynthetic routes. The aerobic desaturase/elongase pathway sequentially introduces double bonds and extends carbon chains via specific desaturase and elongase enzymes. In parallel, an anaerobic polyketide synthase–like PUFA synthase assembles PUFAs through modular condensation reactions, independent of molecular oxygen. Species such as Thraustochytrium, Aurantiochytrium and Schizochytrium have been shown to harbour both systems, with gene clusters encoding Δ4, Δ5 and Δ6 desaturases alongside multifunctional PUFA synthase complexes. Environmental factors—temperature, oxygen levels and nutrient status—profoundly influence pathway activity, lipid content and PUFA profiles. Transcriptomic analyses have revealed regulatory networks that coordinate precursor supply (acetyl-CoA, malonyl-CoA, NADPH) with enzyme expression, while metabolic engineering and bioprocess optimisation are accelerating protist-based production. Given the ecological significance of marine PUFAs in food webs and their rising demand for nutraceutical and industrial applications, elucidation of these biosynthetic mechanisms underpins sustainable manufacture of omega-3 fatty acids.

Research from Nature Portfolio

Studies have demonstrated the co-production of DHA and squalene in Schizochytrium limacinum grown on lignocellulosic hydrolysates, achieving DHA contents above 66% of total lipids and squalene titres nearing 1 g/L through optimisation of substrate concentration and bioreactor conditions. In Aurantiochytrium sp., comparative fermentations under nitrogen starvation versus oxygen limitation revealed that nitrogen depletion upregulates fatty acid synthase genes for saturated lipid accumulation while PUFA synthase gene expression remains relatively constant, offering strategies to tailor lipid fractions. These investigations advance understanding of metabolic regulation and highlight feedstock diversification and co-product valorisation for cost-effective omega-3 production.

Biosynthesis of Polyunsaturated Fatty Acids in Marine Protists publication trend

The graph below shows the total number of articles in biosynthesis of polyunsaturated fatty acids in marine protists across all publications each year (not limited to Nature Index journals).

Technical terms

Polyunsaturated fatty acids (PUFAs): Fatty acids containing more than one cis-double bond in their hydrocarbon chain.

Fatty acid desaturase: Enzyme that introduces double bonds at specific positions within fatty acid chains.

Elongase: Enzyme that extends the carbon chain of fatty acids by two carbons per catalytic cycle.

Polyketide synthase (PUFA synthase): Multifunctional enzyme complex that assembles long-chain PUFAs via iterative condensation reactions, independent of oxygen.

Transcriptome: Complete collection of RNA transcripts expressed by an organism under defined conditions.

References

1. Metabolic engineering to enhance biosynthesis of both docosahexaenoic acid and odd-chain fatty acids in Schizochytrium sp. S31. Biotechnology for Biofuels and Bioproducts (2019).
2. Biosynthetic mechanism of very long chain polyunsaturated fatty acids in Thraustochytrium sp. 26185[S]. Journal of Lipid Research (2016).
3. Lipid and DHA-production in Aurantiochytrium sp. – Responses to nitrogen starvation and oxygen limitation revealed by analyses of production kinetics and global transcriptomes. Scientific Reports (2019).
4. Co-production of DHA and squalene by thraustochytrid from forest biomass. Scientific Reports (2020).
5. Enhancement of docosahexaenoic acid production by overexpression of ATP-citrate lyase and acetyl-CoA carboxylase in Schizochytrium sp.. Biotechnology for Biofuels and Bioproducts (2020).
6. Analysis of Δ12-fatty acid desaturase function revealed that two distinct pathways are active for the synthesis of PUFAs in T. aureum ATCC 34304. Journal of Lipid Research (2012).