Effects of gradual and sudden changes of salinity and light supply for astaxanthin production in Haematococcus pluvialis (Chlorophyceae)

Astaxanthin, a carotenoid naturally synthesized by Haematococcus pluvialis, is economically important for the nutraceutical, pharmaceutical and food industries due to its high antioxidant and anti-inflammatory properties. We investigated astaxanthin accumulation in H. pluvialis after stepwise versus suddenly increased light supply and salt (NaCl) concentrations. Light was increased from 75 to 150, and then to the final intensity of 350 mu mol photons m(-2) s(-1) in three-day intervals. The effect of gradually increased salt concentration was examined with two steps from 0.2 to the final concentration of 0.8 % (w/v) in three-day intervals. The overall induction period for astaxanthin accumulation was 13 days. Out of all treatments, stepwise increased light supply resulted in highest cell viability and highest astaxanthin accumulation with 15.76 +/- 0.88 mg g(-1) dry mass. It is an energy-saving, appropriate strategy to achieve optimal astaxanthin accumulation. It moreover resulted in the least biomass loss, which is caused by the provided stress conditions.