Effects Of Carbon/Nitrogen-Ratio On The Growth And Astaxanthin Accumulation Of Haematococcus Pluvialis

Astaxanthin is a red ketocarotenoid which has high antioxidant ability and has been widely used in the aquaculture, nutraceutical, cosmetic and food industries. The green microalga Haematococcus pluvialis accumulates the highest astaxanthin content compared with all other potential organism sources. In this work, we studied the effects of different carbon sources, different carbon/nitrogen-ratios and carbon sources combination on the growth and astaxanthin accumulation of H. pluvialis. Different concentrations of CO2, sodium bicarbonate, sodium acetate and glucose were used in algal cultivation. The results showed that inorganic carbon sources were more efficient for the cell growth and higher concentration of CO2(600ppm) can significantly promote the growth and photosynthesis of H. pluvialis, with the maximum cell density and growth rate of35.83×104cells/mL and0.30d-1respectively.1.25g/L sodium acetate addition increased average cell diameter from20.87μm to25.88μm and this group gained higher astaxanthin content within single cell (9.26pg/cell). The growth and astaxanthin content of H. pluvialis were affected by the C/N ratio in the medium. The cell grew well when both carbon and nitrogen were plenteous, and cell culture showed higher total chlorophyll content with relative lower C/N.While the astaxanthin content within a single cell increased with the medium C/N increase. After cells were cultured for12days, the astaxanthin content reached10.93pg/cell when the concentrations of CO2and KNO3were600ppm and1g/L respectively, which was the highest among all C/N testing groups. And the value of astaxanthin content was6.69pg/cell with no nitrogen added. A combination use of CO2aeration for biomass accumulation and sodium acetate addition for astaxanthin induction was established. The maximum astaxanthin content,4.57mg/L (14.68pg/cell), was obtained at ACI group (cells in sodium acetate group with CO2aeration and illumination) after15days. As proved, this simple, economical and efficient carbon source supplementation method can be applied for astaxanthin production by using H. pluvialis.