Optimized two-stage process of Haematococcus sp. for enhanced astaxanthin and essential fatty acids accumulation

The present study evaluated a two-stage process of Haematococcus sp. to enhance the nutritional value by astaxanthin and fatty acid accumulation. Initial screening of different growth media during the green stage, focusing on enhanced biomass yield, showed the maximum growth using flory medium with a biomass yield of 0.991 g L⁻¹ at the 30^th day. Bold’s basal medium (BBM) exhibited the second highest biomass yield of 0.856 g L⁻¹ at the 21^th day. Due to faster growth, BBM presented the highest recorded biomass productivity of 0.040 g L⁻¹ day⁻¹, an increase of 21.2 % higher than flory and 207.7 % higher than the standard WHM medium. In the red stage, focused on maximizing astaxanthin yield, high-temperature stress was found to be the most effective stressor, leading to a significant increase in astaxanthin production by 217 % in comparison to the control. Interestingly, this stress condition also enhanced the total cellular fatty acids accumulation by 82.4 % over the control. However, a reduction in stearic acid (18:0) and alpha-linolenic acid (18:3n3) proportions under stress conditions was observed, suggesting the induction of metabolic shifts which involve reallocation of resources towards astaxanthin biosynthesis. These findings demonstrate a successful optimization strategy for Haematococcus sp. cultivation, which could be applied in industrial settings to enhance astaxanthin yield while reducing the production costs by avoiding vitamin supplementation, thereby helping in sustainable bio-based economy development.