Carotenoid content of chlorophycean microalgae: factors determining luteinaccumulation in Muriellopsis sp (Chlorophyta)

Fifteen strains of chlorophycean microalgae have been investigated with reg ard to their carotenoid profile. Lutein, beta-carotene and violaxanthin wer e present in virtually all of the strains, lutein, in general, being the mo st abundant carotenoid, whereas canthaxanthin and astaxanthin were found in some strains only. Chlorella fusca SAG 211-8b, Chlorococcum citriforme SAG 62.80, Muriellopsis sp., neospongiococcum gelatinosum SAG B 64.80 and Chlo rella zofingiensis CCAP 211/14 exhibited high lutein levels, the latter str ain containing in addition substantial amounts of astaxanthin. Muriellopsis sp. was further characterized, since besides a high lutein content (up to 35 mg l(-1) culture), it had the highest growth rate (up to 0.17-0.23 h(-1) ) and maximal standing cell density (up to 8 x 10(10) cells l(-1) culture). These levels of lutein are in the range of those reported for astaxanthin in Haematococcus and for beta-carotene in Dunaliella, microalgae of recogni zed interest for the production of these carotenoids. Lutein content of Mur iellopsis sp. increased during the exponential phase of growth, with the hi ghest value being recorded in the early stationary phase. Maximum levels of lutein in Muriellopsis sp. cultures were recorded at 20-40 mM NaNO3, 2-100 mM NaCl, 460 mu mol photon m(-2) s(-1), pH 6.5 and 28 degrees C, condition s which were, in general, also optimal for cell growth. Growth-limiting con ditions, such as pH values of 6 or 9 and a temperature of 33 degrees C, wer e found to stimulate carotenogenesis in Muriellopsis sp. This strain repres ents a potential source of lutein, a commercially interesting carotenoid of application in aquaculture and poultry farming, as well as in the preventi on of cancer and diseases related to retinal degeneration. (C) 2000 Elsevie r Science B.V. All rights reserved.