Novel CrtW carotenoid ketolase are provided that are useful for the
production of ketocarotenoids. The ketolases genes of the present
invention exhibit low homology in comparison to other CrtW ketolases
previously reported. Expression of the carotenoid ketolases in
heterologous hosts enabled production of canthaxanthin and astaxanthin.
Coexpression experiments using divergent crtW genes resulted in increased
production of the desired ketocarotenoids.