Oxidation von Sesquiterpenen
Sesquiterpenoids are a highly diverse class of natural products that have historically provided a rich source for discovery of biologically active small molecules, such as fragrances, flavourings or pharmaceuticals. These substances are typically produced in low abundance in the host plants, and their isolation consequently suffers from low yields. Furthermore, their chemical syntheses can also be difficult and often involve toxic compounds. For these reasons an attractive alternative strategy is the development of an efficient recombinant microbial whole-cell biocatalyst. A key step here is establishing methods to carry out cytochrome P450-based oxidation chemistry in vivo. As a model process selective oxidation of (+)-valencene to (+)-nootkatone with recombinant E. coli cells will be developed. Due to its pleasant grapefruit-like aroma and other interesting sensory characteristics, (+)-nootkatone represents a highly sought-after specialty chemical, with a current market value of ~ 4000 € per kg.
The main goal of the project is the development of a recombinant E. coli whole-cell biocatalyst for the biooxidation of (+)-valencene to (+)-nootkatone. In our previous work P450 CYP109B1 from Bacillus subtilis was implemented and optimised for allylic oxidation of (+)-valencene to a mixture of nootkatol and (+)-nootkatone, with a preference for the alcohol. In the actual project the focus will be on further oxidation of nootkatol to the final product (+)-nootkatone in vivo and optimisation of the E. coli whole-cell system regarding cofactor regeneration, high productivity and efficient product recovery.