Torularhodin and torulene are the major contributors to the carotenoid pool of marine Rhodosporidium babjevae (Golubev)

Abstract

A carotenoid-producing yeast strain, isolated from the sub-arctic, marine copepod Calanus finmarchicus, was identified as Rhodosporidium babjevae (Golubev) according to morphological and biochemical characteristics and phylogenetic inference from the small-subunit ribosomal RNA gene sequence. The total carotenoids content varied with cultivation conditions in the range 66-117 microg per g dry weight. The carotenoid pool, here determined for the first time, was dominated by torularhodin and torulene, which collectively constituted 75-91% of total carotenoids under various regimes of growth. Beta-carotene varied in the range 5-23%. A high-peptone/low-yeast extract (weight ratio 38:1) marine growth medium favoured the production of torularhodin, the carotenoid at highest oxidation level, with an average of 63% of total carotenoids. In standard yeast medium (YM; ratio 1.7:1), torularhodin averaged 44%, with increased proportions of the carotenes, torulene and beta-carotene. The anticipated metabolic precursor gamma-carotene (beta,psi-carotene) constituted a minor fraction (<or=8%) under all conditions of growth.