The effect of salinity shock on the growth and rapid light curve of dunaliella salina

Abstract

To confirm the effect of hypersaline shock on the growth of Dunaliella salina, the rapid light curves and chlorophyll fluorescence in D. salina with a NaCl upshift from 80 to 160, 240 and 320 g·L−1, respectively, were measured. Results showed that the photosynthetical saturated light of Dunaliella salina was downregulated to deal effectively with the severe NaCl increase from 80 to 160, 240 and 320 g·L−1. Dunaliella salina can deal effectively with the cells’ rapid increase in NaCl from 80 to 160 g·L−1 by heat dissipation to dissipate the excess energy. Salinity with 240–320 g·L−1 NaCl led to overproduction of QA− and the destruction of the PSII acceptor side, causing inhibition of photosynthetic electron transport. Dunaliella salina can also manage the abrupt rise in NaCl concentration from 80 to 240 g·L−1 by accumulating the amount of β‐carotene and glycerol per cell. However, Dunaliella salina cannot effectively manage the rapid increase in NaCl from 80 to 320 g·L−1 due to the stronger inhibition and impaired of the PSII acceptor side. It is suitable to shade D. salina cells to 500 and 800 μmol·m−2·s−1 when cells are exposed to a severe NaCl shift from 80 to 160 g·L−1 and 80 to 240 g·L−1. NaCl ranged from 80 to 240 g·L−1 favoured the growth and carotenoid content of D. salina; however, the survival rate and photosynthetic activity were lowered by the sudden increase in NaCl.

Influence of desalination concentrate medium on microalgal metabolism, biomass production and biochemical composition

“…The response mechanism of each microalga has been shown to vary when subjected to different salinities in which most microalgae generally secrete glycerol to counterbalance osmotic shock 42 . In response to salinity stress, microalga cells undergo a series of cascades involving the production of ROS.…”

“…The response mechanism of each microalga has been shown to vary when subjected to different salinities in which most microalgae generally secrete glycerol to counterbalance osmotic shock. 42 In response to salinity stress, microalga cells undergo a series of cascades involving the production of ROS. These ROS play a crucial role in adjusting the activity of photosynthesis and respiration, as well as enhancing the activity of detoxifying enzymes within the cells.…”

“…35 Functionally, when D. salina is exposed to a hyperosmotic shock by changing the concentration of NaCl, its metabolism is preceded by a rapid recovery of intracellular Na + concentration with a rebalancing synthesis of glycerol within the cell via DHAP/glycerol-3-phosphate dehydrogenase. 41,42 Still, the DHAP for glycerol synthesis is mainly derived from starch catabolism. 39 Microelement calcium also has an important role in the signalization response to osmotic stress, via Ca 2+ intracellular channels in D. salina and C. reinhardtii.…”

“…salina cells, 40 while a sudden increase in salinity in freshwater microalga Chlamydomonas reinhardtii cultivation can lead to the overproduction of saturated fatty acid 35 . Functionally, when D. salina is exposed to a hyper‐osmotic shock by changing the concentration of NaCl, its metabolism is preceded by a rapid recovery of intracellular Na + concentration with a rebalancing synthesis of glycerol within the cell via DHAP/glycerol‐3‐phosphate dehydrogenase 41,42 . Still, the DHAP for glycerol synthesis is mainly derived from starch catabolism 39 …”

Light supply and mineral nutrition conditions as optimization factors for outdoor mass culture of carotenogenic microalga Dunaliella salina

“…Most of cultivation parameters during large-scale D. salina cultivation in open photobioreactors under naturally changing temperature and illumination conditions are unstable (Bonnefond, Moelants, Talec, Bernard & Sciandra, 2016;Borowitzka & Vonshak, 2017;Del Campo, García-González & Guerrero, 2007). Thus, photoinhibition processes begin to prevail at an excessive amount of light energy, which significantly reduces the division rate of D. salina cells, especially in the cells exposed to salinity increase (Polle & Melis, 1999;Park, Lee & Jin, 2013;Qin, Li, Zhang & Liu, 2021). Moreover, such conditions usually lead to the substantial temperature increase in photobioreactors, which also has a negative impact on the algae growth rate (Liang et al, 2020).…”