Isolation and characterization of carotenoid producing yeasts from Qassim region

Abstract

The aim of the present study was to characterize and identify yeasts capable of producing carotenoids. Strains were classified and identified through morphological and physiological characteristics as well as, biochemical and nutritional requirements. Yeast strains were isolated from the surfaces of different fruits, vegetables and dairy products of Qassim region, Kingdom of Saudi Arabia. Thirty six yeast strain isolates were selected on the basis of their ability to produce yellow to red pigments. The samples were grown at incubation temperature of 30ºC in Erlenmeyer flasks, containing growth medium of YM broth. After incubation period of 48 hours, the isolated yeast strains were inoculated in Petri dishes with YM agar, and incubated at 30ºC for 120 hours. The yeast colonies, which presented yellow to red coloration, were transferred to culture tubes containing YM agar, and incubated at 30ºC for 72 hours. These highly pigmented yeasts were re-isolated in Petri dishes with YM agar and then transferred to tubes with GPYM agar. Identification through morphological and reproduction characteristics, along with physiological and biochemical tests, classified two strains as Rhodotorula mucilaginosa and Rhodotorula glutinis. The main carotenoids extracted from them were identified by HPLC analysis as β- carotene and torulene. The isolated yeast strain of Rhodotorula mucilaginosa showed potential as promising microorganism for the commercial production of carotenoids.