Civstallization is an established method used in the initial recovery of organic acids and amino acids, and more widely used for final purification of a diverse range of compounds.
[n citric acid production, the filtered broth is treated with Ca(OH)2 so that the relatively insoluble calcium citrate crystals will be precipitated from solution. Checks are made to ensure that the Ca(OH)2 has a low magnesium content, since magnesium citrate is more soluble and would remain in solution. The calcium citrate is filtered off and treated with sulphuric acid to precipitate the calcium as the insoluble sulphate and release the citric acid. After clarification with active carbon, the aqueous citric acid is evaporated to the point of crystallization (Lockwood and Irwin, 1964; Sodeck et al., 1981; Atkinson and Mavituna, 1991). Crystallization is also used in the recovery of amino acids; Samejima (1972) has reviewed methods for glutamic acid, lysine and other amino acids. The recovery of cephalosporin C as its sodium or potassium salt by crystallization has been described by Wildfeuer (1985).
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