Industrial Production of the Cell Protectant Ectoine: Protection Mechanisms, Processes, and Products
Hans Jorg Kunte,
Erwin A. Galinski.
Bacteria, Archaea and Eukarya can adapt to saline environments by accumulating compatible solutes in order
to maintain an osmotic equilibrium. Compatible solutes are of diverse chemical structure (sugars, polyols, amino acid
derivatives) and are beneficial for bacterial cells not only as osmoregulatory solutes, but also as protectants of proteins by
mitigating detrimental effects of freezing, drying and high temperatures. The aspartate derivative ectoine is a wide spread
compatible solute in Bacteria and possesses additional protective properties compared with other compatible solutes, and
stabilizes even whole cells against stresses such as UV radiation or cytotoxins. The protective properties of ectoine for
proteins can be explained by its strong (kosmotropic) interaction with water and subsequent exclusion from protein
surface, the decrease of the solubility of the peptide backbone and the strengthening of intramolecular hydrogen bonds
(secondary structures). The stabilizing and UV-protective properties of ectoine attracted industry, which saw the potential
to market ectoine as a novel active component in health care products and cosmetics. In joint efforts of industry and
research large-scale fermentation procedures have been developed with the halophilic bacterium Halomonas elongata
used as a producer strain. The two key technologies that allow for the annual production of ectoine on a scale of tons are
the bacterial milking procedure and the development and application of ectoine-excreting mutants (“leaky” mutant). The
details of these two procedures including the strain development and fermentation processes will be introduced and
current and future applications of ectoine will be discussed.
Keywords: Bacterial milking, batch fermentation, continuous culture, ectoine excretion, Hofmeister effect, kosmotrope,
“leaky” mutant, osmophobic effect, protein protection, preferential exclusion.
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