Microbial Carotenoids Production: Strains, Conditions, and Yield Affecting Factors

The research and development of carotenoid production has a long history, and interest in this group of pigments has not decreased to this day. Six existing carotenoids are considered industrially important: astaxanthin, β-carotene, lutein, zeaxanthin, canthaxanthin, and lycopene. These carotenoids have a wide range of applications and are used as additives in food and beverages, feed, nutraceuticals, pharmaceuticals, and cosmetics products due to their bioactive and pigmentation properties. Currently, the global pigment market is dominated by chemically synthesized carotenoids. Carotenoids derived from natural sources such as plants and microorganisms are not as popular or widespread. Currently, the market of natural carotenoids is mainly represented by microalgae Haematococcus pluvialis, Dunaliella salina, Botryococcus braunii, fungus Blakeslea trispora, yeast Phaffia rhodozyma and bacteria Paracoccus carotinifaciens. These microorganisms produce astaxanthin, β-carotene, canthaxanthin, and lycopene. Several yeast and bacteria species from Rhodotorula, Sporobolomyces, Sporidiobolus, Gordonia, and Dietzia genus can potentially become sources of carotenoids on an industrial scale, but available technologies still need improving. This paper reviews strategies for increasing the competitiveness of fungal and bacterial carotenoid production. Strategies such as selecting carotenogenic strains, using low-cost substrates, stimulating the synthesis of carotenoids by adding trace elements, TCA intermediates, NaCl, H₂O₂, light irradiation, and optimization of fermentation conditions such as pH, temperature and aeration are considered.