Enhancement of fucoxanthin accumulation in Phaeodactylum tricornutum by light quality and intensity shift strategy

Diatoms exhibit great potential for biofuels, high value-added production from wastewater and promoting carbon neutrality. Fucoxanthin is identified as the main carotenoid in diatoms, which is a photosynthetic pigment with a variety of biological activities and physiological functions. Light quality is essential for microalgal growth, photosynthesis and intracellular metabolism, and microalgal cells often respond to the effects of light to regulate their biochemical makeup. Therefore, goal of this research was to develop a strategy for altering light quality and intensity to maximize fucoxanthin generation, in line with the photoresponsive traits of Phaeodactylum tricornutum and to investigate the underlying mechanism based on metabolomics and transcriptomics. Different light qualities, culture strategies, light intensities and light ratios were explored and optimized, and the findings illustrated that the optimal fucoxanthin production was observed when under the red light during the initial phase, followed by a transition to the blue-green mixed light (60μmol m⁻² s⁻¹) conditions in the subsequent phase. Transcriptome and metabolome analyses showed that the light shift strategy provided sufficient energy and precursors for cell growth and fucoxanthin accumulation by enhancing the EMP pathway, TCA cycle, and light-harvesting complex in photosynthetic system. The present study provides a feasible strategy and mechanism to customize the light quality regulatory strategy to enhance biosynthesis of target bioactive compounds, and provides a theoretical basis for further investigation of the regulatory mechanism, which can provide a foundation for microalgal fucoxanthin production.