By Maria Cristina P. P. Reis Mansur

Text written for the “Scientific Communication Topics” subject of the Post-Graduate program in Science (Microbiology) at the Paulo de Góes Microbiology Institute

Carotenoid pigments of various colors produced by microorganisms.

Color is one of the first characteristics perceived by the human eye. It awakens our senses on observing nature in relation to the flowers, fruits, vegetables and algae. Currently, there is a search for natural products to add color to food, textiles, cosmetics and medicines. Microorganisms are an excellent alternative for the commercial exploitation of pigments for industry.

Carotenoids are natural dyes responsible for the red, orange and yellow colors in many vegetables, flowers and plants in general. Also their beneficial effects on health have aroused the interest of the scientific community worldwide. The food, pharmaceutical and cosmetic industries have invested in research on new sources and applications of these important molecules. Studies on carotenoids also seek solutions for industrial processes; solutions to develop methods to maintain the appropriate levels of these substances and their properties in foods and not lose them during processing and storage.

There are about 900 different types of carotenoids of natural origin. They have more than 40 carbons in their structural formula arranged in a series of conjugated double bonds. They are divided into two classes: carotenes which have only carbon and hydrogen atoms, and oxocarotenoides or xanthophylls which besides carbon and hydrogen have at least one oxygen atom.

Carotenoids have a wide range of applications in cosmetics, and one of them is protection against photo-oxidative processes. They can act as effective antioxidants through the capture of singlet oxygen and peroxyl radicals. There is growing evidence showing that carotenoids protect our skin against damage caused by excessive exposure to solar radiation.

Carotenoids, which are present in various foods, are capable of capturing free radicals that are in imbalance in our bodies and which cause negative effects to human skin, such as macular degeneration, cancer, mutations, premature aging, as well as cataracts and arteriosclerosis.

Carotenoids are synthesized only by plants, algae, fungi and yeast type prokaryotes (bacteria and archaea). The biological activity of carotenoids is linked to its structure. Carotenoids are also common in bacteria isolated from most areas exposed to solar radiation, for example, in the Sahara and Antarctica and show potential photo-protective properties.

Biotechnological production of carotenoids has various advantages due to the possibility of using low cost substrates and only a small area is required for their production and easy control of the culture conditions. There is no interference from environmental conditions such as climate, season or soil composition. Many microorganisms produce carotenoids, but not all of them have industrial applications. Also, due to concern over the use of chemical additives in foods, there is an increasing interest in carotenoids obtained naturally by biotechnological processes.

Canthaxanthin is a carotenoid pigment frequently used in food; it provides a reddish color to the food. It is also used in animal husbandry, salmon feed and canary feathers acquire their red color from it. The bacteria Rhodococcus maris, Micrococcus roseus, Gordonia jacobaea, Bradyrhizobium sp. and Haloferax alexandrinus and the cyanobacteria: Anabaena variabilis, Aphanizomenon flos-aqua and Nostoc commune produce this pigment.

 Astaxanthin is a powerful antioxidant, about 10 times more effective than other carotenoids. As a natural nutritional component, astaxanthin is also found in dietary supplements. Some microorganisms are of industrial interest and producers of this carotenoid, include the bacteria Pseudomonas sp., Paracoccus sp. and Halobacterium Salinarium; the fungi and yeast Phaffia rhodozyma and Xanthophyllomyces dendrohous; and the microalgae Haematococcus pluvialis.

Beta carotene, a natural orange pigment acts as an antioxidant and is one way to obtain vitamin A in the human body indirectly. As a fee radical inhibitor, it prevents premature aging, benefits night vision, boosts immunity, gives skin elasticity, increases the brightness of the hair and strengthens nails, besides acting on fat metabolism. Beta carotene when transformed into vitamin A helps in the formation of melanin, an endogenous sunscreen pigment of ultraviolet rays and it is responsible for tanning the skin. The microorganisms of industrial interest that are producers of this pigment are the bacteria: Pseudomonas putida; microalgae: Dunaliella salina, Spirulina; filamentous fungi: Blakeslea trispora, Phycomyces blaskeleeanus and Mucor circinelloides as well as the yeast: Rhodotorula glutinis.

References:

GABANI, P. & SINGH, O. V. Radiation-resistant extremophiles and their potential in biotechnology and therapeutics. Applied Microbiology and Biotechnology, 97:993–1004, 2013.

GARCIA-PICHEL, F.& GAO, Q. Microbial ultraviolet sunscreens. Reviews Nature/Microbiology, 9: 791-802, 2011.

OLIVEIRA, C. G. Extração e caracterização do betacaroteno produzido por Rhodotorula glutinis tendo como substrato tendo o suco de caju. Universidade Federal do Ceará, Fortaleza, 2010.

VALDUGA, E.;TATSCH, P. O.; TIGGEMANN, L.; TREICHEL, H.; TONIAZZO, G.; ZENI, J.; DI LUCCIO, M. Produção de carotenoides: micro-organismos como fonte de pigmentos naturais. Quimica Nova, 32 (9): 2429-2436, 2009.