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.

Optimization of carotenoid extraction of a halophilic microalgae.

Dunaliella parva can produce abundant carotenoids under certain conditions. This paper optimized the extraction efficiency of carotenoids from D. parva. Different organic solvents were examined to determine the most suitable solvent for the extraction. After the determination of the solvent (dimethylsulfoxide, DMSO), the extraction conditions including time, temperature, and volume were then optimized to maximize the extraction efficiency of carotenoids from D. parva using response surface methodology. DMSO was identified as the most suitable solvent. The optimal extraction conditions were as follows: temperature of 57.2°C, time of 11.35 min, the volume of 410 µl, and the optimal extraction efficiency reached 0.517‰. The results showed that the optimal extraction efficiency (0.517‰) improved 31.69% in comparison to the initial extraction efficiency (0.3926‰). In addition, The optimal levels of three influence factors (temperature of 57.2°C, time of 11.35 min, volume of 410 µl) decreased compared with the initial levels (temperature of 60°C, time of 20 min, volume of 1000 µl). In this paper, Central Composite Design (CCD) was used to optimize the extraction efficiency of carotenoids from D. parva, which would lay the groundwork for the extraction and utilization of carotenoids from D. parva in the future.