Terpenoids are one of the largest classes of plant secondary metabolites featuring many commercially relevant products. They are primarily used as food-flavors or fragrances, but some terpenoids, like artemisinic acid, are also important pharmaceuticals.
Today most terpenoids are extracted from plants they naturally occur in. Due to their low concentration in plant biomass, large cultivation areas are needed to cover demand. Some terpenoids can also be produced synthetically, using petrochemical starting materials. Only in a few cases biotechnological approaches have been successfully used for the production of terpenoids.
Surprisingly, despite their chemical diversity, many terpenoids only require two main classes of enzymes for their biosynthesis from the common building blocks IPP and DMAPP, cyclases and oxygenases. While cyclases can generally be expressed and used in prokaryotes like E. coli oxygenases naturally occur as membrane-bound protein complexes. For functional expression in E. coli soluble versions of these proteins are required, as well as compatible reductases. Expression of these proteins also place significant strain on the energy metabolism of E. coli. We are addressing these problems by creating fusion constructs of the oxygenase and reductase proteins, as well as increasing the availability of NADPH.
Clearly these plant products offer many opportunities for synthetic biology to make their production both more sustainable and more economical. We, the iGEM team Hamburg, want to join many other researches in making terpenoids more accessible.
