The effect of light intensity versus light dose on the antioxidant activity of two strains of Ulva lacinulata

The genus Ulva, described as a good source of antioxidants known for its antibacterial properties and associated with the capacity to adapt to different environments and high growth rates has justified the increasing interest in its large-scale production. . While extensive research has been done on optimizing the extraction of Ulva's bioactive compounds, few studies were conducted on increasing or optimizing antioxidant activity of Ulva spp. during cultivation. Our study aimed to investigate an energy-saving cultivation method for optimizing Ulva lacinulata by testing the impact of light dose and light intensity on its antioxidant activity. Two geographically different strains (NE-Atlantic and Mediterranean) were observed for 5 days under two light intensities (70 or 185 µmol photons m-2 s-1) with the same light dose (4 mol photons m-2 d-1). Samples were collected at different times to evaluate the variation of antioxidant activity (using the ABTS radical decolorisation assay). A strain-dependent response was observed between the NE-Atlantic strain which had significantly higher antioxidant activity after 5 days under the saturating-light, while the Mediterranean strain was not significantly impacted, suggesting that light dose may significantly affect antioxidant activity in certain Ulva spp.