Directed Evolution of Carotenoid Synthases for the Production of Unnatural Carotenoids

Directed evolution is a well-established strategy to confer novel catalytic functions to the enzymes. Thanks to the relative ease of establishing color screening, carotenogenic enzymes can be rapidly evolved in the laboratory for novel functions. The combinatorial usages of the evolvants result in the creation of diverse set of novel, sometimes unnatural carotenoids. This chapter describes the directed evolution of diapophytoene (C₃₀ carotenoid) synthase CrtM to function in the foreign C₄₀ pathway, and the use of the CrtM variants thus obtained for the production of novel backbone structures.