Dynamics of β-carotene and fucoxanthin of tropical marine Navicula sp. as a response to light stress conditions

We investigated the dynamics of beta-carotene and fucoxanthin produced by the tropical marine Navicula sp. that were cultured indoors and outdoors. To obtain high biomass and carotenoid levels, the growth of Navicula sp. in three different nitrogen media (ammonium, urea, and nitrate medium) was evaluated. Navicula sp. showed the most growth in the nitrate medium with a ratio of total carotenoid to chlorophyll a of 1.94 observed on the 7th d. When Navicula sp. growth reached the stationary phase, the ratio of total carotenoid to chlorophyll a increased due to chlorophyll damage. The biomass productivity of Navicula sp. cultivated indoors and outdoors was 153 +/- 3 and 93 +/- 3 mg dried cell L-1 culture d(-1), respectively. Under light stress conditions, the Navicula sp. cell size was reduced. Among Navicula sp. carotenoids, the amount of beta-carotene and fucoxanthin expressed by the cell in response to light stress was very dynamic. The fucoxanthin content of Navicula sp. decreased from 5.40 +/- 0.05 (indoor) to 2.61 +/- 0.06 (outdoor) mg g(-1) dried biomass. However, the beta-carotene content of Navicula sp. increased from 19.99 +/- 0.16 (indoor) to 24.08 +/- 0.16 (outdoor) mu g g(-1) of dried biomass, which indicates the importance of beta-carotene for the photoprotection of cells.