Screening of microalgae and cyanobacteria strains for α-tocopherol content at different growth phases and the influence of nitrate reduction on α-tocopherol production

Tocopherols (vitamin E) are only synthesized by photosynthetic organisms and have wide applications in cosmetics and as dietary supplements in human nutrition and aquaculture. Tocopherols from microalgae and cyanobacteria are rarely investigated, and little is known about their contents. Therefore, 130 strains of cultured microalgae and cyanobacteria were analyzed for alpha-tocopherol content under various culture conditions. The growth phase had a significant effect on content of alpha-tocopherol. Maximal amounts were observed at the stationary growth phase. Reduction of nitrate concentration in media caused an increased production of alpha-tocopherol. The contents were significantly enhanced when the nitrate concentration was reduced to one fourth in culture media used. The content of alpha-tocopherol was found to reflect phylogenetic relationships at the level of classes, with classes of Rhodophyta and Cyanobacteria accumulating the lowest contents. Within each class, contents varied widely at the species level emphasizing the importance of extensive screening procedures for the identification of strains with high alpha-tocopherol contents.