Enhancement of polyunsaturated fatty acids and total carotenoid production in microalgae by ultraviolet band A (UVA, 365 nm) radiation

Two microalgae, Porphyridium cruentum and Platymonas subcordiformis , were subjected to a 3-day exposure of ultraviolet band A (UVA) radiation at 365 nm (～1.32-1.35 W/m(2)) and photosynthetically active radiation (PAR) (～11.56-11.62 W/m(2)) followed by a 3-day UVA-free (exposure to PAR only) treatment. UVA inhibited the growth of P. subcordiformis and P. cruentum during the UVA-exposure period. Significant increases (p < 0.05) of total polyunsaturated fatty acids (PUFAs), saturated fatty acids (SFAs), and lipid content were found in P. cruentum during the UVA exposure period, whereas such increases in P. subcordiformis were observed only at the end of the UVA-free period. Concentrations of individual PUFAs including linoleic acid, eicosatrienoic acid, and eicosapentaenoic acid as well as total carotenoids were significantly increased (p < 0.05) at different stages of the UVA treatment in both microalgae. UVA (365 nm) radiation has the potential application for producing microalgal biomass rich in PUFAs and carotenoids as a natural functional ingredient.