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The mysterious colors of Dunaliella salina: How did this algae give salt lakes their color?
Dunaliella salina is a single-celled green algae that is particularly adapted to living in extremely salty environments such as salt lakes and salt evaporation ponds. This algae is known for its ability to produce large amounts of carotenoids and has antioxidant activity. It is a major producer of extreme salt environments worldwide and is also widely used in cosmetics and dietary supplements.
History
Dunaliella salina was named in 1838 by Emanoil C. Teodoresco from Romania, and the algae was first scientifically reported by Michel Felix Dunal in salt evaporation ponds in France. He initially named the organism Haematococcus salinus and Protococcus. In 1905, Teodoresco and Clara Hamburger of Heidelberg, Germany, fully described the organism as a new genus and species. Since Teodoresco was the first to publish his research results, he is generally considered to be the original contributor to this classification.
Habitat
In such a high salt concentration environment, only a handful of organisms can survive. D. salina has been able to survive to this point because it has high concentrations of beta-carotene to protect itself from strong light, while also maintaining high concentrations of glycerol to resist osmotic pressure. Many people believe that the color of pink lakes comes from the influence of this algae, as they can be found in many pink lakes and the substances in them appear in various shades of pink. However, research conducted in Lake Hillier, Australia since 2015 has revealed the presence of several species of halotrophic bacteria and archaea in the lake, almost all of which also contain some pink, red or salmon-colored pigments.
Morphological characteristics
Species of the genus Dunaliella are morphologically similar to Chlamydomonas reinhardtii, the main difference being that Dunaliella lacks a cell wall and contractile vacuoles. This alga has two flagella of equal length and a cup-shaped chloroplast that usually contains a central cytoplasm. Its chloroplasts can store a large amount of β-carotene, making the algae appear orange-red. Beta-carotene appears to protect the organism from the effects of long-term UV radiation. The shape and symmetry of D. salina vary depending on its environment. Due to the lack of a rigid cell wall, this organism is particularly sensitive to osmotic pressure. Glycerol serves as a means of maintaining osmotic balance and enzyme activity. D. salina is able to retain high concentrations of glycerol by maintaining a low permeability cell membrane and synthesize large amounts of glycerol from starch when external salt concentrations are high, which is one of the reasons why it can thrive in extremely high salinity environments. one.
Reproduction and life cycle
D. salina can reproduce asexually by division of motile plant cells, or sexually by fusion of two equal gametes to form a single zygote. Although D. salina can tolerate saline environments, studies have shown that its sexual reproductive activity is significantly reduced at high salt concentrations (>10%) and is stimulated at low salt concentrations. Sexual reproduction begins when the flagella of two D. salina come into contact, followed by fusion of the two gametes into a zygote. The zygotes of D. salina are extremely hardy, able to survive in both freshwater and dry environments. After germination, the zygote can release up to 32 haploid daughter cells.
Commercial Use
D. salina is one of the major producers in extremely saline environments worldwide.
β-carotene
Since the establishment of the first D. salina cultivation factory in the Soviet Union in 1966, commercial cultivation of D. salina for β-carotene production has become a successful case of halobiotechnology. Different techniques are used, ranging from low-tech extensive lagoon culture to precisely controlled culture at high cell densities.
Antioxidants and nutritional supplements
Due to its high content of beta-carotene, D. salina is a popular provitamin A food supplement and cosmetic additive. In addition, D. salina may be a source of vitamin B12.
Glycerin
Attempts have been made to exploit the high concentrations of glycerol accumulated by D. salina for commercial production. Although it is technically possible to produce glycerol from D. salina, economic feasibility is low and there are currently no biotechnological operations that produce glycerol from this algae.
This vibrant algae has attracted not only the attention of the scientific community, but also the interest of the industry. Given its wide range of application potential, how will Dunaliella salina affect our lives and the environment in the future?
