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Dunaliella salina is a favourable source of high lipid feedstock for biofuel and medicinal chemicals. Low biomass output from microalgae is a significant barrier to industrial-scale commercialisation. The current study aimed to determine how photosynthetic efficiency, carbon fixation, macromolecular synthesis, accumulation of neutral lipids, and antioxidative defence (ROS scavenging enzyme activities) of D. salina cells were affected by different light intensities (LI) (50, 100, 200, and 400 µmol m -2  s -1 ). The cells when exposed to strong light (400 µmol m -2  s -1 ) led to reduction in chlorophyll a but the carotenoid content increased by 19% in comparison to the control (LI 100). The amount of carbohydrate changed significantly under high light and in spite of stress inflicted on the cells by high irradiation, a considerable increase in activity of carbonic anhydrase and fixation rate of CO 2 were recorded, thus, preserving the biomass content. The high light exposed biomass when subjected to nitrogen-deficient medium led to increase in lipid content (59.92% of the dry cell weight). However, neutral lipid made up 78.26% of the total lipid while other lipids like phospholipid and glycolipid content decreased, showing that the lipid was redistributed in these cells under nitrogen deprivation, making the organism more appropriate for biodiesel/jet fuel use. Although D. salina cells had a relatively longer generation time (3.5 d) than other microalgal cells, an economic analysis concluded that the amount of carotenoid they produced and the quality of their lipids made them more suited for commercialization., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Selenium (Se) is an essential element for living systems, however, toxic at higher levels. In the present study, Dunaliella salina cells were exposed to different Se concentrations for their growth (EC 50 195 mg L- 1 ) as well as Se accumulation. The cells exposed to 50 mg L- 1 Se showed photoautotrophic growth parallel to control and accumulated 65 μg Se g- 1 DW. A decrease in photosynthetic quantum yield, chlorophyll content, and the increase in intracellular reactive oxygen species, proline content, and lipid peroxidation accompanied by higher neutral lipid accumulation, were recorded at higher Se level. The enzymes superoxide dismutase and catalase played a pivotal role in antioxidative defense. Heterogeneity in accumulated carotenoids at varying concentrations of selenium was prevalent. The cells exposed to 200 mg L- 1 Se resulted in the disorganization of organelles. Thus, the Se enriched biomass obtained at 50 mg L- 1 may be explored for bio-fortification of food and feed., Competing Interests: Declaration of competing interest There is no conflict of interest among authors., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Mass cultivation of Dunaliella salina was standardized in a flat plate photobioreactor followed by a vertical flat plate photobioreactor. Maximum biomass productivity (14.95 ± 0.43 mgL -1 d -1 dry cell weight) was achieved in the latter at inoculum concentration of OD 680nm  = 0.1, 100 µmolm -2 s -1 light illumination and 1.0 L min -1 aeration. Semicontinuous operation with varying KNO 3 and NaHCO 3 concentrations resulted highest biomass productivity (17.85 ± 0.55 mgL -1 d -1 ) at 0.50 mM NaHCO 3 and 15 mM KNO 3 . However, maximum lipid (16.36 ± 1.18% dry cell weight) was achieved at 0.75 mM NaHCO 3 and 10 mM KNO 3 . Flocculation studies employing potash alum, FeCl 3 ·6H 2 O or pH showed harvesting efficiencies exceeding 90% in 0.75 mM potash alum or FeCl 3 ·6H 2 O or pH 11, but they yielded low concentration factor (<5) and were detrimental (Fv/Fm < 0.50). A combination of 0.50 mM FeCl 3 ·6H 2 O and pH 9 was found as most suitable flocculating strategy with maximum concentration factor (>14) and least damaging (Fv/Fm > 0.54)., (Copyright © 2018 Elsevier Ltd. All rights reserved.)