Introduction of a green algal squalene synthase enhances squalene accumulation in a strain of sp. PCC 6803.

Squalene is a triterpene which is produced as a precursor for a wide range of terpenoid compounds in many organisms. It has commercial use in food and cosmetics but could also be used as a feedstock for production of chemicals and fuels, if generated sustainably on a large scale. We have engineered a cyanobacterium, sp. PCC 6803, for production of squalene from CO. In this organism, squalene is produced via the methylerythritol-phosphate (MEP) pathway for terpenoid biosynthesis, and consumed by the enzyme squalene hopene cyclase (Shc) for generation of hopanoids. The gene encoding Shc in was inactivated (Δ) by insertion of a gene encoding a squalene synthase from the green alga , under control of an inducible promoter. We could demonstrate elevated squalene generation in cells where the algal enzyme was induced. Heterologous overexpression of genes upstream in the MEP pathway further enhanced the production of squalene, to a level three times higher than the Δ background strain. During growth in flat panel bioreactors, a squalene titer of 5.1 ​mg/L of culture was reached.