Research on the Influence of Orthogonal Design Optimized Elicitor Combinations on Fucoxanthin Accumulation in...

Fucoxanthin, a carotenoid with notable pharmaceutical potential, has attracted significant attention due to its efficient accumulation in marine microalgae and the importance of optimizing its induction conditions. In this study, Phaeodactylum tricornutum was employed as a model organism to screen optimal conditions for fucoxanthin accumulation using a three-factor, four-level orthogonal design. Furthermore, the underlying mechanisms related to photosynthetic physiology and gene regulation were explored. The results revealed that both glycine (Gly) and light intensity significantly enhanced fucoxanthin content (p < 0.05). The optimal condition (Combination C: 0.50 g L^-1 Gly, 36 μmol photons·m^-2·s^-1, 12 h light/12 h dark) yielded a fucoxanthin content of 0.87 μg g^-1, representing a 35% increase compared to the control. Meanwhile, Combination p (0.50 g L^-1 Gly, 36 μmol photons·m^-2·s^-1, 24 h light/0 h dark) significantly improved cell density (5.11 × 10⁶ cells mL^-1; +18%) and fucoxanthin yield (4.10 μg L^-1; +47%). Analysis of photosynthetic parameters demonstrated that the non-photochemical quenching coefficient (NPQ) was suppressed. Gene expression profiling showed that Combination C upregulated photosynthetic genes (psbA, rbcL, rbcS) by up to 2.36-fold, while Combination P notably upregulated fcpb (7.59-fold), crtiso, and pds. Principal component analysis identified that rbcS and pds are key regulatory genes. These findings demonstrate that Gly, light intensity, and photoperiod synergistically regulate the expression of genes involved in photosynthesis and carotenoid biosynthesis, thereby promoting fucoxanthin accumulation. This work provides valuable insights and a theoretical basis for optimizing fucoxanthin production in support of marine drug development.