Staged cultivation enhances biomass accumulation in the green growth phase of Haematococcus pluvialis.

An innovative staged cultivation (SC) method was proposed to overcome the limiting factors associated with the growth of Haematococcus pluvialis in the green growth phase. This strategy led to a 1.16-fold increase in biomass concentration. Light wavelength, nutrient concentration and extracellular metabolite were identified to be key limiting factors when cells of H. pluvialis were in the low, medium, and high cell density sub-phase, respectively. A mix of red and white light (2:1) was demonstrated for the first time to accelerate cell growth in the low cell density sub-phase. Shortage of nutrients during the medium density sub-phase was overcome with a fed-batch approach maintained at stable pH, while the inhibitory effect of extracellular metabolites during the high density sub-phase was overcome with replacement cultivation. The findings of the present study suggest SC in the green growth phase may be a promising approach to significantly enhance biomass accumulation in culturing microalgae.