Omega-3 fatty acids are an essential part of the human diet (reference) . Human beings, and all larger organisms cannot synthesize ω-3 fatty acids as they lack a Δ15 desaturase to create a double bond at the correct location. Certain microrganisms, such as microalgae and cyanobacteria, do contain this desaturase and can thus directly synthesize ω-3 fatty acids (Arts et al, 2009). Their anabolic product can then enter the food chain – algae are eaten by fish, and seafood is the main source of ω-3 for humans (Tonon et al, 2002).

However, overfishing is a serious problem in the world’s oceans already, and the human population is estimated to rise to a up to NUMBER (reference) . Additionally, global warming will cause a further reduction in the availability of ω-3 (Arts et al, 2009): at higher temperatures, microalgae produce less ω-3 desaturated fatty acids. Desaturated carbon chains cause a lower melting temperature in the membrane, which the microorganism wants to avoid by using more saturated fatty acids in their membranes (Garwin, Cronan, 1980) . Thus, the combination of declining fish stock and a decrease in overall ω-3 fatty acids is making the continuation of supply for human nutrition a relevant issue.

Harvesting algae directly is costly and ineffective (Borowitzka, 1997), so there is much potential in expressing a metabolic pathway for ω-3 fatty acid synthesis in E. coli, which is cheaper and more accessible.