Torularhodin and Torulene: Bioproduction, Properties and Prospective Applications in Food and Cosmetics - a Review

Torularhodin and torulene are two widespread microbial carotenoids with relatively few studies, as compared to other nutraceutical carotenoids such as β-carotene, lycopene and astaxanthin. Several genera of microorganisms produce it in high concentration (up to 0.1% of the cell dry weight), probably as a protection against photooxidation and free radicals. These pigments, which differ by a terminal carboxylic group, have provitamin-A activity and, being red, have potential use as food and cosmetic color additives. Several factors affect the biosynthesis of these substances, including: the composition of culture media, light irradiation, which may enhance the carotenoid production up to 25% of the non-irradiated cultures, and temperature, which changes the carotenoid balance towards more of the acidic carotenoid (torularhodin) or the hydrocarbon (torulene). The biomass may be directly extracted using non polar solvents such as hexane or a hexane-acetone mixture, without need of cell disruption. Extensive purification is not needed for using the pigments as food or cosmetic additives, but it is still necessary to evaluate the bioactivity of the pigments in humans.