Abstract
Carotenoids are produced by photosynthesizing organisms, i.e. plants and algae, as well as some bacteria, protists and fungi. Their role lies mainly in the function of complementary photosynthetic pigments and antioxidants. Carotenoids are distinguished according to their structure into carotenoids of the hydrocarbon type, e.g. α-, β- and γ-carotene and oxygen derivatives – xanthophylls, among which astaxanthin, which excels in its antioxidant and nutraceutical properties, is the most important. It is used as a dietary supplement both in human nutrition and in the aquaculture and poultry industry, as a nutritional supplement in salmonid and hen farming. Many works have focused on the search for natural sources of astaxanthin as an alternative to synthetic astaxanthin. In nature, very few astaxanthin producing organisms are known in non-minor amounts, with green alga Haematococcus pluvialis and the yeast Xanthophyllomyces dendrorhous (anamorph Phaffia rhodozyma) being the most promising microorganisms for the biotechnological production of this xanthophyll. In this review we focus on the biosynthesis and carotenogenesis including the regulation mechanisms, generation of hyperproducing mutants by random mutagenesis and, last but not least, also metabolic engineering (genetic techniques). Attention is also paid to the optimization of fermentation conditions.
Highlights
Astaxanthin belongs to carotenoids, i.e. compounds derived from tetraterpenes having 40 carbon atoms
Astaxanthin produced by algae, e.g. freshwater Haematococcus pluvialis, produces more than 90% of the isomer 3S, 3’S, while the yeast Xanthophyllomyces dendrorhous produces more than 90% of the 3R, 3’R isomer, see Figure
3.1 Microbial production of astaxanthin in X. dendrorhous It is currently believed that the main function of carotenoids in X. dendrorhous is to protect yeast from the damage caused by oxidative stress
Summary
Astaxanthin belongs to carotenoids, i.e. compounds derived from tetraterpenes having 40 carbon atoms. Astaxanthin is found above all in primary sources – in some algae and yeasts and in secondary sources – marine invertebrates (small crustacean plankton (krill), shrimp, crayfish, etc.), salmon, trout and waterfowl feathers. It is the cause of the red color of salmon and the red color of cooked crustaceans. The sources of astaxanthin are either sea krill (see synthesis, including hundreds of intermediates (Britton above) or cultivated algae (mainly Haematococcus pluvi- et al, 1996). The disadvantage of this synthesis, as menalis) or yeasts, e.g. X_dendrorhous, formerly P. rhodozyma. A preparative chiral column, but for economic reasons (the cost of a column with such a special chiral phase), this procedure is currently not feasible
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