Sustainable Cultivation of Haematococcus pluvialis for the Production of Natural Astaxanthin

Haematococcus pluvialis is a microalga with the ability to accumulate high quantities of astaxanthin. However, the large freshwater footprint and the requirement of external nutrient supply are issues in its commercial-scale cultivation. In the present study, synthetic dairy wastewater was employed as an alternative culture media for H. pluvialis under varying light intensities to determine the best lighting conditions for biomass and astaxanthin accumulation. The highest biomass concentration ($1.359 \pm 0.013\ \mathrm{g}/\mathrm{L}$) and astaxanthin concentration ($20.783 \pm 0.105\ \text{mg}/\mathrm{L}$) was achieved in the culture supplied with 3250 lux light intensity during the growth stage. Nevertheless, the highest specific growth rate ($0.0625 \pm 0.000$ /day) and cellular astaxanthin content $(1.696 \pm 0.007\%)$ were observed in the culture supplied with 4000 lux during the growth phase. It was also observed that the total lipid content of cultures did not vary significantly with light intensity. Moreover, it was observed that total lipid content of residual H. pluvialis decreased significantly after astaxanthin extraction. Nonetheless, H. pluvialis showcased considerable potential of nutrient removal efficiency, achieving over 90% reduction of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP). Thus, it could be speculated that cultivation of H. pluvialis under moderate light intensities could yield astaxanthin and lipid-rich biomass simultaneous to phycoremediation.