Abstract:
The current study investigated methods culturing green motile cells of Haematococcus pluvialis under red light on cell density, cell growth rate and cell activity. In red light, the stationary growth phase in batch culture maintained for long time, and the cell photosynthetic activity maintained stable high. There was no neutral lipid accumulation in the cell growth in red light. Biomass yields from a semi-continuous culture of 20% medium renew rate was 57% higher than those from the batch culture. The variation of nutrient absorption rate and chlorophyll fluorescence parameter showed that cellular stress regulation started earlier in batch culture than those in semi-continuous cultures. The cell growth rate and photosynthetic activity were negatively related to the initial cell density in a batch culture. Culture of lower initial density had higher growth rate and higher photosynthetic activity. The effects of CO2 on the cultures under red light or under white light were conditionally dependent. Adding CO2 increased maximum biomass by 54%. The growth rates increased as while, however, that in the red light was higher (0.223/d) than that in white light (0.198/d). The pH values were not related with the light quality under both red light and white light, and pH decreased to the suitable level of pH 78. Chlorophyll parameter Fv/Fm significantly increased by red light with CO2 addition while it is not mediated by white light. Cell size significantly decreased by red light with CO2 addition while it was no regulated by white light. These results revealed that the method of intermittent semi-continuous culture for green motile cells of H. pluvialis had higher cell yield with high activity, which is a plausible strategy in astanxanthin industry.