Physiological changes of microalga Dunaliella parva under the treatment of PEG, CaCl2.

Carotenoids are antioxidants, which reduce various chronic diseases of human, and have many industrial applications. The halophilic Dunaliella parva (D. parva) is rich in carotenoids. The compounds CaCl2 and PEG are the popular metabolic enhancers. To further enhance carotenogenesis, D. parva was treated with two compounds polyethylene glycol (PEG) and CaCl2. Application of CaCl2 and PEG enhanced the carotenoids contents and the antioxidant activities of carotenoids compared to control group (no treatment of CaCl2 or PEG). The highest carotenoids contents were obtained by treating D. parva with 40 ppm CaCl2 (3.11 mg/g dry weight, DW) and 80 ppm PEG (2.78 mg/g DW) compared with control group (1.96 mg/g DW). When D. parva was treated with 40 ppm CaCl2 and 80 ppm PEG, protein contents reached the highest values (90.28 mg/g DW and 89.57 mg/g DW) compared to that of control group (73.42 mg/g DW). The antioxidant activities of carotenoids samples were determined. Generally, the antioxidant activities of carotenoids from D. parva treated with PEG and CaCl2 were superior to that of control group. The antioxidant activities of carotenoids mainly contained reducing power, hydroxyl radical scavenging activity and superoxide radical scavenging activity. The reducing powers of carotenoids extracts from 20 ppm CaCl2 group (2.07%/mg carotenoids) and 120 ppm PEG group (1.59%/mg carotenoids) were significantly higher than that of control group (<1.25%/mg carotenoids). The superoxide radical scavenging activities of carotenoids extracts from 40 ppm CaCl2 group (70.33%/mg carotenoids) and 80 ppm PEG group (65.94%/mg carotenoids) were significantly higher than that of control group (<55%/mg carotenoids). This paper laid a foundation for massive accumulation of carotenoids in microalga D. parva.