Light-independent, astaxanthin production by the green microalga Haematococcus pluvialis under salt stress

Green vegetative cells of Haematococcus pluvialis grew heterotrophically on acetate in the dark. When vegetative cells were stressed with 0.1% NaCl, MSCl2, KCl or CaCl2, cyst formation was induced rapidly in the dark. Salt-stressed, 8-day old brown-red cyst cells in the dark contained astaxanthin at 30 pg/cell (9 mu g/ml). It was concluded that salt stress causes both cyst formation and carotenoid biosynthesis in the dark.