Screening for a low-cost Haematococcus pluvialis medium reveals an unexpected impact of a low N/P ratio on vegetative growth
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The green alga Haematococcus pluvialis is the current best source of natural astaxanthin, a high-value carotenoid. Traditionally, the production process of astaxanthin by this algae is achieved by a two-stage system: during the first stage, vegetative “green” cells are produced and then converted, in the second stage, into cysts that accumulate astaxanthin. In this work, a medium screening strategy based on the mixing of a three-component hydroponic fertilizer was applied to identify a new formulation optimized for the vegetative stage. A maximal and high cell density of 2 × 106 cells mL−1 was obtained in a medium containing a high level of phosphate relative to nitrate, resulting in a N/P ratio much lower than commonly used media for H. pluvialis. In this medium, cells remained at the vegetative and motile stage during a prolonged period of time. Both high cell density culture and motile stage persistence was proved to be related to the N/P feature of this medium. We conclude that the macrozoid stage of H. pluvialis is favored under high-P and low-N supply and that low-cost hydroponic fertilizers can be successfully used for achieving high density cultures of vegetative cells of H. pluvialis.
KeywordsHaematococcus pluvialis Culture media optimization Phosphate supply Nutrient-induced fluorescence transients
This research was funded by WINNOMAT2 program, Service Public de Wallonie, DGO6, Grant N°71/6662. A.F. is grateful to F.R.I.A. for the award of research fellowships. F.F. is a Senior Research Associate of the Fonds de la Recherche Scientifique, F.R.S–FNRS. Authors are grateful to Dr. P. Cardol and anonymous reviewers for helpful comments on an earlier draft of this manuscript.
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