Productive encystment of Haematococcus pluvialis by controlling a specific irradiation rate in a photoautotrophic induction system for astaxanthin production

A productive photoautotrophic induction system was established for the production of antioxidative astaxanthin by the green microalga Haematococcus pluvialis. During photoautotrophic induction, N-deprived Haematococcus cells were sensitive to the specific irradiation rate (I) on transformation to astaxanthin-rich cyst cells. Compared with the CO2 condition, the optimum specific irradiation rate (I-opt) was confined within narrow limits between light limitation and inhibition. Maximal astaxanthin synthesis in H. pluvialis was promoted under a 5 % CO2 environment and unsynchronized illumination with a specific irradiation rate of 80 mu mol photon/g . s, yielding an accumulation rate of 4.3 mg/g . day. This result indicates that a favorable CO2 concentration and controlled specific irradiation rate leads to the productive encystment of H. pluvialis and enhanced astaxanthin synthesis.