Carotenoids profile of the unicellular Eustigmatos cf. polyphem (Eustigmatophyceae) and beta-carotene production of the microalga in bubble column and large flat panel bioreactors were studied. The microalga which contained beta-carotene, violaxanthin and vaucheriaxanthin as the major carotenoids accumulated large amount of beta-carotene. The beta-carotene production of this microalga in the bubble column bioreactor was considerable, with the maximum intracellular beta-carotene content reaching 60.76 mg g(-1), biomass reaching 9.2 g L-1, and beta-carotene yield up to 470.2 mg L-1. The beta-carotene productions in two large flat panel bioreactors were relatively lower, whereas over 100 mg beta-carotene L-1 was achieved. Besides, high light intensity helped to accumulate intracellular beta-carotene and biomass. Deficient nitrate supply inhibited biomass growth, though it helped to accumulate beta-carotene. Our results first proved that E. cf. polyphem was a potential source and producer of beta-carotene, making it an interesting subject for further beta-carotene study or commercial exploration. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.