Fatty acids, carotenoids, and tocopherols from microalgae: Targeting the accumulation by manipulating the light during growth

Microalgae are a promising source for new functional food products due to their ability to synthesize various bioactive compounds. The intensity and spectral distribution of light affect metabolic processes in microalgae, which consequently affects the accumulation of these bioactive compounds. The aim of this study was to investigate the effect of light intensity, the wavelength range of LED, and UVB exposure on the content of fatty acids, carotenoids, and α-tocopherol in four microalgal species: Arthrospira maxima, Chlorella minutissima, Rhodomonas salina, and Nannochloropsis oceanica. Different light regimes (3 levels of light intensity—100, 400, and 800 μmol photons m⁻² s⁻¹; three monochromatic LEDs—blue, red, and green; and UVB exposure at the dose 3 kJ m⁻² day⁻¹) were applied after microalgae reached their late-exponential growth phase, in order to investigate potential factors that might trigger the accumulation of those high-value compounds. The light intensity of 400 μmol photons m⁻² s⁻¹ mostly favoured carotenoid production, while 800 μmol photons m⁻² s⁻¹ favoured lipid and α-tocopherol accumulation. Rhodomonas salina demonstrated an increase by ~ 10% in the relative content of omega-3 fatty acids after UVB exposure. Illumination of C. minutissima by green LED resulted in considerable levels of carotenoids (6.2 ± 0.2 mg g⁻¹ DM) and α-tocopherol (673–677 μg g⁻¹ DM). Red light significantly enhanced PUFAs synthesis in R. salina, with a nearly doubled proportion of EPA (8.8 ± 0.3% of total FA) compared to the control, whereas green light enhanced the accumulation of α-tocopherol 20-fold. Acquired data suggested that microalgal cells with unique physiology could be produced by tailoring light quality and quantity.