Effects of light spectra on growth and compositions of biomass, fatty acids, and pigments in three typical microalgae from different phyla

The growth and nutrients of photosynthetic organisms are significantly influenced by light spectra, yet this relationship is not well-understood in microalgae. Herein, we studied three microalgae species—Chaetoceros sp., Isochrysis galbana, and Tetraselmis helgolandica—distinguished by their pigments. We exposed them to seven light spectra, including white (control), red, orange, green, blue, violet, and full spectrum. The results showed distinct responses in the three microalgae to varying light spectra. Optimal growth occurred under blue, violet, and white lights for Chaetoceros sp., I. galbana, and T. helgolandica, respectively, while orange, red, and green lights inhibited growth. Notably, green light significantly increased the protein content in all three microalgae. Carbohydrate and lipid content exhibited species-specific responses: the highest carbohydrate accumulation was achieved for Chaetoceros sp. under red light (73.27±1.45 mg/g), I. galbana under orange light (122.89±12.28 mg/g), and T. helgolandica under blue light (43.62±2.79 mg/g). Meanwhile, the highest lipid content was obtained under violet light for Chaetoceros sp. and I. galbana (250.80±7.27 and 320.23±5.75 mg/g, respectively), and under green light for T. helgolandica (255.12±31.19 mg/g). Furthermore, violet light greatly promoted the accumulation of polyunsaturated fatty acids in all three microalgae. Specific pigment compositions also responded to variations in light spectra. For instance, the diadinoxanthin content in Chaetoceros sp. increased significantly under orange light (194.77±13.78 µg/g), while chlorophyll-a content in I. galbana increased significantly under violet and blue lights ((88.84±33.46)–(141.38±1.64) µg/g), and in T. helgolandica under red, green, and blue lights ((1 485.04±190.46)–(1 886.60±387.42) µg/g). Additionally, I. galbana exhibited the highest fucoxanthin, diadinoxanthin, and β-carotene contents under white light. In conclusion, our results highlight the species-specific impact of light spectra on microalgae growth and nutrients, providing valuable guidance for flexible application of light spectra in microalgal production to enhance yields and target specific nutrients.