Carotenogenesis in Haematococcus pluvialis cells induced by light and nutrient stresses

Abstract

The objective of this work was to evaluate the responses of Haematococcus pluvialis cells to the carotenogenesis induction process, under light and nutrition stress. Cells were acclimated during 15 days in WC medium, with aeration with synthetic, filtered atmospheric air and flow rate of 100 mL min^‑1, light intensity of 50 μmol photons m^‑2 s^‑1, photoperiod of 12 hours, and temperature of 23°C. The following two treatments were compared: cultivation under the described conditions, but with increase of light intensity up to 350 μmol photons m^‑2 s^‑1; and cultivation under the same conditions as the previous treatment, but with aeration containing 4% CO₂. The treatments were done in triplicate, during ten days. With the addition of CO₂ and the increment in lighting, an increase was observed in the carotenoids/chlorophyll ratio and cell biomass. Cells stopped dividing on the second day of stress, when nitrate became limiting, and significantly increased their biovolume. The excretion of organic carbon and the concentration of astaxanthin increase in response to the addition of CO₂. Stress by light intensity combined with CO₂ addition optimizes carotenogenesis in H. pluvialis and increases astaxanthin production.