Light-emitting diodes-a plus on microalgae biomass and high-value metabolite production

Light plays a crucial role in photosynthetic microalgae, and its quality is a key point for biomass production and the variability of the organisms' biochemical composition, with blue and red, the light bands being the most effectively absorbed by green algae. Recently, light-emitting diodes (LEDs) have emerged as an alternative that allow a better modulation of algal metabolism. The aim of this work was to study the effects of blue and red LEDs on antioxidant capacity, biomass productivity (P-x) and carotenoid and fatty acid content over time in a microalga known to be a producer of antioxidant compounds, Scenedesmus obliquus M2-1. Monochromatic blue (B) and red (R) LEDs and two dichromatic combinations of blue and red (BR (40:60) and BR (50:50)) were tested, and fluorescent lamp (FL) was used as a control. Then, supplementation effects of near-infrared radiation (NIR) LEDs were assessed in the same in parameters. Results show that B induced higherP(X)and higher content in fatty acids when compared with other LED conditions tested. Scenedesmus obliquus M2-1 under R attained a higher antioxidant capacity and under BR (40:60) a higher carotenoid production, particularly lutein and beta-carotene, when compared with that of FL. NIR supplementation in BR (40:60) and R treatments enhanced P-X and fatty acid content, changing the profile of antioxidant compound production over time, but keeping the maximum concentration. Additionally, NIR supplementation decreased the total carotenoid production. This study reveals that the use of R and BR (40:60) LEDs are a useful tool to enhance the production of carotenoids in S. obliquus M2-1.