Dunaliella salina
| Dunaliella salina | |
|---|---|
 | |
| Orange-colored Dunaliella salina within sea salt | |
| Scientific classification | |
| Kingdom: | Plantae |
| Phylum: | Chlorophyta |
| Class: | Chlorophyceae |
| Order: | Volvocales |
| Family: | Dunaliellaceae |
| Genus: | Dunaliella |
| Species: | D. salina |
| Binomial name | |
| Dunaliella salina | |
Dunaliella salina is a type of halophile green micro-algae especially found in sea salt fields. Known for its antioxidant activity because of its ability to create large amount of carotenoids, it is used in cosmetics and dietary supplements. Few organisms can survive in such highly saline conditions as salt evaporation ponds. To survive, these organisms have high concentrations of β-carotene to protect against the intense light, and high concentrations of glycerol to provide protection against osmotic pressure. This offers an opportunity for commercial biological production of these substances.
History
Dunaliella salina was named by EC Teodoresco of Bucharest, Romania after its original discoverer, Michel Felix Dunal, who first sighted the organism in saltern evaporation ponds in Montpellier, France in 1838. He initially named the organism Haematoccocus salinus and Protococcus. The organism was fully described as a new, separate genus simultaneously by Teodoresco and Clara Hamburger of Heidelberg, Germany in 1905. Teodoresco was the first to publish his work, so he is generally given credit for this categorization.
Morphology
Species in the Dunaliella genus are morphogically similar to Chlamydomonas' with the main exception being that Dunaliella lack both a cell wall and a contractile vacuole. Dunaliella has two flagella of equal length and has a single cup-like chloroplast that often contains a cental pyrenoid. In D. Salina, the chloroplast can hold large amounts of B-carotene, which makes appear orange-red. D. salina is unique in that it contains very large amounts of cis-B-carotene, a strong oxidant, along with all-trans-B-carotene as opposed to just all-trans-B-carotene. The B-carotene appears to protect the organism from long-term UV radiation that D. salina is exposed to in its typical environments. D. salina comes in various shapes and symmetries depending on the conditions in its current environment.
Reproduction and Life Cycle
D. Salina can reproduce asexually through division of motile vegetative cells and sexually through the fusion of two equally gametes into a singular zygote. Even though D. Salina can survive in salinic environments, Martinez et al. determined that sexual activity of “D. Salina” significantly decreases in higher salt concentrations (>10%) and is induced in lower salt concentrations. Sexual reproduction begins when two D. Salina’s flagella touch leading gamete fusion. The D. Salina zygote is extraordinarily hardy and can survive exposure to freshwater and to dryness. After germination, the zygotes release up to 32 haploid daughter cells.
β-carotene
From a first pilot plant for D. salina cultivation for β-carotene production established in the USSR in 1966, the commercial cultivation of D. salina for the production of β-carotene throughout the world is now one of the success stories of halophile biotechnology. Different technologies are used, from low-tech extensive cultivation in lagoons to intensive cultivation at high cell densities under carefully controlled conditions. Although D. salina produce β-carotene in a high salt environment, Archaea such as Halobacterium, not D. salina, are responsible for the red and pink coloring of salt lakes.[1] Occasionally, orange patches of D. salina colonies will crop up.
Glycerol
D. salina lacks a rigid cell wall, which makes organism susceptible to osmotic pressure. Glycerol is used as a means by which to maintain both osmotic balance and enzymatic activity. D. salina maintains a high concentration of glycerol by producing a cell membrane with low permeability to glycerol and synthesizing large quantities of glycerol from starch as a response to high extracellcular salt concentration, which is why it tends to thrive in highly salinic environments. Attempts have been made to exploit the high concentrations of glycerol accumulated by D. salina as the basis for the commercial production of this compound. Although technically the production of glycerol from D. salina was shown to be possible, economic feasibility is low and no biotechnological operation exists to exploit the alga for glycerol production.
See also
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Wikimedia Commons has media related to Dunaliella salina. |
References
- ↑ Oren, Aharon (2005). "A hundred years of Dunaliella research: 1905-2005". Saline Systems 1: 2. doi:10.1186/1746-1448-1-2. PMC 1224875. PMID 16176593.