Fed-batch culture of astaxanthin-rich Haematococcus pluvialis by exponential nutrient feeding and stepwise light supplementation

A fed-batch culture process followed by subsequent photoautotrophic induction was established for the high density culture of astaxanthin-rich Haematococcus pluvialis using a CO₂-fed flat type photobioreactor under unsynchronized illumination. Fed-batch culture was performed with an exponential feeding strategy of the growth-limiting nutrients, nitrate and phosphate, concurrently with the stepwise supplementation of light depending on the cell concentration. During the growth phase, a biomass of 1.47 g/L was obtained at a biomass productivity of 0.33 g/L/day. Photoautotrophic induction of the well-grown vegetative cells was performed consecutively by increasing the light intensity to 400 μmol photon/m²/s, while keeping the other conditions in the CO₂-fed flat type photobioreactor fixed, yielding an astaxanthin production of 190 mg/L at an astaxanthin productivity of 14 mg/L/day. The proposed sequential photoautotrophic process has high potential as simple and productive process for the production of valuable Haematococcus astaxanthin.