Phenol phycoremediation by Haematococcus pluvialis coupled with enhanced astaxanthin and lipid production under rac-GR24 supplementation for enhanced biodiesel production

The present study evaluated the impact of rac-GR24 on biomass and astaxanthin production under phenol stress coupled with biodiesel recovery from Haematococcus pluvialis. Phenol supplementation showed negative impact on growth, where the lowest biomass productivity of 0.027 g L^-1 day^?1 was recorded at 10 µM phenol, while 0.4 µM rac-GR24 supplementation showed the highest recorded biomass productivity of 0.063 g L^-1 day^?1. Coupling 0.4 µM rac-GR24 at different phenol concentrations confirmed the potential of rac-GR24 to mitigate the toxic effect of phenol by enhancing yield of PSII yield, RuBISCo activity, and antioxidant efficiency, which resulted in improved phenol phycoremediation efficiency. In addition, results suggested a synergistic action by rac-GR24 supplementation under phenol treatment where rac-GR24 enhanced lipid accumulation, while phenol enhanced astaxanthin production. Dual supplementation of rac-GR24 and phenol showed the highest recorded FAMEs content, which was 32.6% higher than the control, with improved biodiesel quality. The suggested approach could enhance the economic feasibility of triple-purpose application of microalgae in wastewater treatment, astaxanthin recovery, and biodiesel production.