Abstract: Background: Some marine bacteria, such as Moritella marina, produce the nutraceutical docosahexaenoic acid
(DHA) thanks to a specific enzymatic complex called Pfa synthase. Escherichia coli heterologously expressing the pfa
gene cluster from M. marina also produces DHA. The aim of this study was to find genetic or metabolic conditions to
increase DHA production in E. coli.
Results: First, we analysed the effect of the antibiotic cerulenin, showing that DHA production increased twofold.
Then, we tested a series of single gene knockout mutations affecting fatty acid biosynthesis, in order to optimize the
synthesis of DHA. The most effective mutant, fabH, showed a threefold increase compared to wild type strain. The
combination of cerulenin inhibition and fabH deletion rendered a 6.5-fold improvement compared to control strain.
Both strategies seem to have the same mechanism of action, in which fatty acid synthesis via the canonical pathway
(fab pathway) is affected in its first catalytic step, which allows the substrates to be used by the heterologous pathway
to synthesize DHA.
Conclusions: DHA-producing E. coli strain that carries a fabH gene deletion boosts DHA production by tuning down
the competing canonical biosynthesis pathway. Our approach can be used for optimization of DHA production in
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