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A New Cell Factory for High-Purity DHA Production

A new metabolic engineering strategy was developed and may be used to produce designer oils for human nutritional supplements.

We have probably seen “DHA” plastered on the front of baby milk powder, but what is it and why is it important? Docosahexaenoic acid, or DHA, is an important nutritional component for brain and visual development in newborns and is useful in treating many diseases.

Currently, oceanic fish oils are a major source of DHA for humans with a DHA content of only about 10 per cent. While strain breeding, fermentation optimisation, and metabolic engineering have been employed to improve the yield and purity of DHA, most studies have only been able to achieve a small effect on DHA purity. However, Aurantiochytrium, owing to its high biomass and high lipid content, has become one of the major alternative sources for DHA production.

Building on their previous work with recombinant Aurantiochytrium, which saw an increase in DHA purity by 18 per cent, researchers from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences developed a combined metabolic engineering strategy to obtain a novel strain producing high-purity DHA. This study was published in the Journal of Agriculture and Food Chemistry.

The strategy involves both disrupting one copy of a gene that will partially deactivate the pathway competing with DHA biosynthesis and overexpressing two proteins–acetyl-CoA carboxylase and diacylglycerol acyltransferase–to increase substrate supply and triacylglycerol synthesis. From this, the researchers obtained a “super” mutant with a DHA purity of 61 per cent in total fatty acids and a content of 331 mg/g dry cell weight, demonstrating the success of the combined metabolic engineering strategy.

Moreover, this strategy may also be used to further improve DHA purity and yield by incorporating more steps like enhancing certain pathways and regulating the expression of key genes.

From this study, an advanced strategy for sustainable high-purity DHA production was developed, yielding a novel strain of Aurantiochytrium with favourable characteristics that would satisfy industrial fermentation and commercial applications. [APBN]

Source: Wang et al. (2021). Obtaining High-Purity Docosahexaenoic Acid Oil in Thraustochytrid Aurantiochytrium through a Combined Metabolic Engineering Strategy. Journal of Agricultural and Food Chemistry.