Chemical inducers regulate ROS signalling to stimulate astaxanthin production in Haematococcus pluvialis under environmental stresses: A review

Natural astaxanthin, a super antioxidant and colorant, is widely applied in the nutrition, cosmetics, pharmaceuticals, food and feed industries. Haematococcus pluvialis is the predominant commercial source of astaxanthin and is being intensively studied to maximize its astaxanthin content and yield. Low productivity and high cost remain the two major drawbacks to the large-scale production of H. pluvialis. Chemical inducers combined with stressful conditions constitute an effective joint strategy to promote increases in the astaxanthin yield of H. pluvialis. This review summarizes the effects of three classes of chemical inducer-regulated reactive oxygen species (ROS), namely, ROS-stimulating, ROS-alleviating and non-influencing ROS, on astaxanthin accumulation, and analyses the underlying mechanisms through which ROS signalling stimulate astaxanthin biosynthesis and modulate stress tolerance in H. pluvialis. Chemical inducers can regulate ROS signalling to elevate astaxanthin enrichment in H. pluvialis under stressful environments, and during this process, carbon redistribution, the antioxidant system, hormone flux or other signalling pathways are modulated. This review will provide a feasible biotechnology for enhancing the economic production of astaxanthin from H. pluvialis through supplementation with food-grade and economical chemical inducers. Furthermore, large-scale optimization and economic feasibility analyses should be conducted in accordance with the current strategy.