The global market for astaxanthin -the red carotenoid responsible for the color of salmon flesh, crustacean shells or flamingo feathers- rises markedly, with a preferential demand for the natural pigment from the microalga Haematococcus pluvialis. Current methodology for the production of astaxantin-rich cells follows a two-stage approach, first producing biomass under optimal growth conditions and then exposing the alga to adverse environmental conditions that promote encystment and accumulation of the carotenoid. An improved methodology involving a one-step-only continuous production strategy has been developed recently. Specific nitrate input and average irradiance are the most relevant parameters in determining the behavior of this continuous system that generates reddish vegetative cells, with astaxanthin representing more than 1% of the dry biomass. Feasibility of the method has been carefully analyzed indoors and verified outdoors in a tubular photobioreactor. Its singular capacity, besides a high quality of the reddish biomass product, made the system a real alternative to the two-stage option generating hard-walled red cysts.

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