Carotenoids are the most widely distributed class of pigments in nature and have essential biological functions in animals. They also impart attractive pigmentation to many farmed animals. Yeasts have desirable properties as a biological source of pigment. The sap of birch tree with regard to some properties is a selective environment for growth of carotenoid producing yeasts. In this study, carotenoid - producing yeasts have been isolated from sap of birch trees in Tees Bisheh valley located in the west of Shahrestanak village.
Taxonomic studies (morphology, fermentation, assimilation reactions and other characteristics) of the isolated yeasts indicate that one of the strains can be identified as a Rhodotroula glutinis with high capability of carotenoid production.