**8. Conclusions**

This review has focused on the carotenoid Ά-ring-modifying enzymes, CrtW, CrtZ and CrtG, derived from the marine bacteria of the ΅-*Proteobacteria* class, and pathway engineering for the production of xanthophylls in *E. coli*, using these enzyme genes. Such pathway engineering researches are performed towards efficient production not only of commercially important xanthophylls such as astaxanthin, but also of xanthophylls minor in nature, which are difficult to synthesize chemically, and expected to have beneficial effects on human health as well as anti-oxidation function. 
