Light-mediated lutein enrichment of an acid environment microalga

Algae fully acclimated to different light intensities express different characteristics. At low light intensities, most algae produce more light-harvesting pigments to improve their photosynthetic efficiency. In contrast, at high light intensities, some algae produce high concentrations of “sunscreen” pigments to protect the cell from exposure to excess ultraviolet and PAR light. Coccomyxa onubensis grows selectively at pH 2.5, which is a competitive advantage for massive production. The alga pigment profile is rich in carotenoids, especially lutein. In this research we studied the effect of low to moderate light intensity shifts on lutein accumulation of C. onubensis cultures, doubly aimed at understanding the light-dependent role of main carotenoids in acid-tolerant microalgae and at developing strategies to induce β-carotene and mainly lutein accumulation with applied purposes. Coccomyxa cells were grown at 50, 140 and 400 μmol photons m− 2 s− 1, reaching their maximum growth rates and carotenoid productivities at 400 μmol photons m− 2 s− 1. Lutein accumulation slightly depended on biomass concentration and maximum productivities of biomass and lutein were achieved in relatively dense cultures of 0.7 and 1 g L− 1. The main results indicate that C. onubensis is a very promising lutein accumulating microorganism if incubated under a suitable cultivation strategy mainly consisting of transferring relatively low biomass concentration cultures either from low to moderate light intensity or from moderate to low light intensity, therefore profiting from either pigment light-capturing or light-dissipation activities.