Relationship Between Culture Factors And Cell Transformation, Astaxanthin Accumulation In Haematococcus Pluvialis

Unicellular fresh-water green alga Haematococcus pluvialis, well known for its great ability to produce astaxanthin (10 000³0 000 mg/kg) under certain conditions, is one of the best microbial sources for commercial production of natural astaxanthin. Astaxanthin is named as "Super Vitamin E" for its powerful antioxidant activity, it's an excellent feed additive, food colorant and a potential medicine in delaying aging and degenerative diseases in humans and animals. It owns a high price in the international market with the number over $3000/kg and demands still far exceed supply. Therefore, the culture of Haematococcus pluvialis for astaxanthin became the subject of intensive research since 1980's. Influences of main environmental factors on cell growth and astaxanthin accumulation in Haematococcus pluvialis were widely issued to get a higher astaxanthin yield. However, these studies reached different or even contradictory conclusions which made it difficult for them to consult each other and brought much confusion to the following researchers. One of the main reasons for this chaos was due to the interfering to the results from the dynamic changes of nutrients added in the beginning of the experiments. Another reason was the co-existence of the three individual processes, cell growth, cell transformation and astaxanthin accumulation per cell, in the culture of Haematococcus pluvialis. Thus, new methods were introduced in our study by eliminating nutrients from the culture medium before each experiment. Effects of light intensity, salinity and temperature respectively on the cell growth, cell transformation and astaxanthin accumulation per cell were studied individually and the main results are listed as below: 1. The existence of nutrients was disadvantageous to the cell transformation and astaxanthin accumulation in each tested strain of Haematococcus pluvialis, this phenomenon is more pronounced in H₃ than in H₀, H₂ showed the least sensibility to the existence of nutrients. 2. In the experimental light intensity range, stronger light is good for cell transformation rate and astaxanthin accumulation although it is unfavorable to cell growth than a weaker one did; H₃ showed a strong resistance to the changes of light intensity in a relatively wide ranges while this is reverse in H₂; the rules of dynamic changes showed a higher amount of astaxanthin production and a higher rate of astaxanthin accumulation. 3. the cell growth of each strain was inhibited when the salinity was lifted while the increase of cell size was promoted under the same time, no obvious effects was showed in cell transformation rate, however, under the higher salinity of over 1% the safe transformation number of the transformation process was decreased hence decreased the total astaxanthin production to a certain degree, as in low salinity cultures it still could get a highest yield among all for the astaxanthin accumulation per cell being promoted under the circumstances accompanied with relatively high non-motile numbers. 4. It was adverse to cell growth while favorable to cell size and cell transformation rate by lifting the culture temperature, effects of temperature on astaxanthin production and accumulation were different in the three strains, a higher astaxanthin production was reached in H0 and H3 under a lower temperature, it brought out both a highest astaxanthin production and a highest astaxanthin accumulation per cell under 25℃ in H2; no distinguished changes were showed in H3 in astaxanthin accumulation per cell under different temperatures probably for its being not sensitive to the temperature changes, contrarily, a strong temperature dependent was showed in H2 in astaxanthin production and astaxanthin accumulation per cell as well as cell size. 5. The main type of motile cell growth was division and agamogenesis (sporangium) and it was budding and agamogenesis (sporangium) as for non-motile cell growth.Based on these studies, it is clear that the optimal conditions for cell growth, cell transformation and astaxa...