Changes of pigments and lipids composition in Haematococcus pluvialis vegetative cell as affected by monochromatic red light compared with white light

Much attention has been paid on studies of astaxanthin accumulation process in Haematococcus pluvialis industry. However, growth of H. pluvialis in motile vegetative stage is still the most important and problematic part in the whole cultivation process, such as low growth rate and cell yields. Motile vegetative cells are extremely sensitive to various stresses which make it difficult to maintain the cells of this state to grow. Previous reports showed that motile vegetative cells may have higher biomass yields if applied monochromatic red light. However, metabolic responses of these cells are not completely understood, which constraints application of this illumination protocol in industry. The aim of this study was to examine how critical biochemical changes of H. pluvialis motile vegetative cells were affected by red light when compared with white light. Variation of photosynthetic pigments composition and lipids were mainly studied. By comparing growth process of cultures in red light and white light, prominent variation of pigments composition and lipids changes were observed. The results showed that, even though cell proliferation was the same during exponential growth phase, variation of photosynthetic pigment composition and lipids occurred. The final biomass of cell number was higher in red light group than in white light group. The variations were significant different. Increase or decrease of major photosynthetic membrane lipids to some extent did not influence photosynthesis of the vegetative cells during this phase. However, vegetative cells under polychromatic white light other than monochromatic red light need further metabolic process to adjust its pigment composition and lipids, possibly this is energetically and biochemically unfavorable for motile vegetative cells to growth under white light, a light condition normally not considered as a stress.