EDTA stands for Ethylene diamine tetra acetic acid (C 10 H 16 N 2 O).
EDTA is a colorless, water-soluble compound often found in the form of either crystals or powder. It acts as a chelating agent for a variety of divalent metal cations and used to stabilize bleach in detergents. As a salt, EDTA is used as an anticoagulant agent. It also has antioxidant properties and reduces blood cholesterol in the body.
EDTA is also used as a food preservative; and as a calcium-disodium salt, it is used in the treatment of lead and other heavy metal poisonings. EDTA is an inhibitor of metalloproteases, at effective concentrations of 1-10M. EDTA acts as a chelator of the zinc ion in the active site of metalloproteases, and can also inhibit other metal ion-dependent proteases such as calcium-dependent cysteine proteases. EDTA may interfere with biological processes that are metal-dependent.
Origin of EDTA
Ferdinand Munz first identified EDTA in the year 1935. He prepared the compound using chloroacetic acid and ethylenediamine. Currently, the synthesis of EDTA is from formaldehyde, ethylenediamine, and sodium cyanide. The combination produces sodium salt that may be subsequently converted to acid forms.
Researches made in the late 1960s by the National Research Council and the National Academy of Sciences indicated EDTA to be effective in treating blocked arteries (arteriosclerosis). Combining with minerals and oral vitamins, it helps in dissolving plaques and other mineral deposits that are associated with the hardening of arteries.
EDTA FOR SPIRULINA CULTIVATION
A mixture of EDTA with other trace elements and a variety of coenzyme factors that enter into photosynthetic reactions act as a growth enhancer for spirulina.
EDTA can be titrated with any trace metal, calcium, magnesium, iron, or zinc. Iron availability for microalgal uptake seems to be largely dependent on levels of chelation.
It is highly recommended that iron be added as the chemically prepared chelated iron salt of EDTA rather than as iron chloride or other iron salts.
Media with manganese as the EDTA-saturating trace metal allow most rapid growth rates whereas, Magnesium as the EDTA-saturating metal does not allow growth, suggesting that Mg does not displace other required trace metals from EDTA-complex.
Since the mixtures allowing maximum growth rate are “underchelated” it appears that the free metals rather than the metal-chelate complexes are utilized by the alga in rapid growth.
EDTA salts are more soluble in water as the pH increases: the more EDTA there is in the salt form, the higher the pH of a water solution, and therefore, the higher the room temperature solubility. This can be achieved by the gradual addition of concentrated sodium hydroxide solution to the EDTA solution.
EDTA may have an additional benefit of reducing precipitation during autoclaving. High concentrations have, however, occasionally been reported to be toxic to microalgae like spirulina. The algal cells of spirulina are harvested in the late log phase of incubation by centrifugation at 10,000 rpm for 10 min at 4 °C and washed thoroughly with 10 mM Na2-EDTA. Ethylene Diamine Tetraacetic Acid Disodium gives spirulina the property to reduce lead accumulation.
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