A Comparison of Constitutive and Inducible Non-Endogenous Keto-Carotenoids Biosynthesis in sp. PCC 6803.

The model cyanobacterium sp. PCC 6803 has gained significant attention as an alternative and sustainable source for biomass, biofuels and added-value compounds. The latter category includes keto-carotenoids, which are molecules largely employed in a wide spectrum of industrial applications in the food, feed, nutraceutical, cosmetic and pharmaceutical sectors. Keto-carotenoids are not naturally synthesized by , at least in any significant amounts, but their accumulation can be induced by metabolic engineering of the endogenous carotenoid biosynthetic pathway. In this study, the accumulation of the keto-carotenoids astaxanthin and canthaxanthin, resulting from the constitutive or temperature-inducible expression of the and genes from , is compared. The benefits and drawbacks of the two engineering approaches are discussed.