Production of Lepidoptera pheromones in yeast cell factories

Crop damage caused by insect pests is a serious problem in agriculture. Conventional control strategies, which rely on the use of chemical insecticides or genetically modified insectresistant plants, come with drawbacks. Pests develop resistance, making these strategies less efficient with time. Additionally, insecticides lack specificity, giving rise to toxic effects in beneficial insects such as bees as well as bigger animals and humans. Insect sex pheromones represent a safe and environmentally friendly alternative. These compounds are naturally produced by certain insects to attract a mating partner. This can be utilised to control pests through mating disruption. Pheromone application in crops will confuse the insects, preventing them from finding each other to mate and reproduce. Pheromones are attractive because they are biodegradable, species-specific compounds, which neither harm biodiversity nor induce resistance development. This thesis describes the development of bio-based production of Lepidoptera pheromones in yeast cell factories. The Lepidoptera order of insects, which comprises moths and butterflies, is interesting from a pest control perspective as it includes major pests such as fall armyworm and cotton bollworm.

To enable bio-based production of insect pheromones, oleaginous yeast Yarrowia lipolytica was used as platform. Metabolic engineering redirected the yeast’s inherent fatty acid metabolism towards pheromone biosynthesis. This was achieved by screening multiple gene candidates from various insects and other organisms and evaluating their effects by fatty acid and fatty alcohol analyses using gas chromatography-mass spectrometry. Genes of interest included fatty acyl-CoA desaturases, fatty acyl-CoA reductases and peroxisomal oxidases, all known for their essential role in moths’ pheromone biosynthesis. Genetic modifications related to decreased formation of triacylglycerides or decreased degradation of fatty acids/alcohols further improved pheromone production. The work presented in this thesis demonstrates how a bio-based yeast platform can be metabolically engineered for production of insect sex pheromones, offering a viable alternative to conventional chemical synthesis. A wider application of pheromones in agriculture will lead to safer and more sustainable pest management.