Physiological responses of microalgae to light and CO₂: insights into pigment production

The aim of this research was to evaluate the combined effects of light intensity, light color, and CO₂ concentration on chlorophyll a, chlorophyll b, and total chlorophyll and carotenoid production in Chlorella sorokiniana and their relationships with cell growth at the photobioreactor scale. A Taguchi L₄ design was applied to assess the impact of these variables systematically. Chlorophylls were quantified via spectrophotometric solvent extraction, and carotenoids were measured on the basis of their absorbance spectra. The highest cell growth (5.89 log₁₀ cells/mL) occurred under violet light, 1.8 × 10^- 4 W/nm, and moderate CO₂ (0.078 L). The maximum chlorophyll production (0.3049 µg/mL) was observed under violet light, 1.8 × 10^- 4 W/nm, and high CO₂ (0.15 L), whereas the highest carotenoid concentration (0.0487 µg/mL) coincided with the conditions promoting maximum growth. These findings indicate that pigment biosynthesis is differentially regulated: chlorophylls respond mainly to the light spectrum, whereas carotenoids are correlated more with metabolic activity than with stress responses. This study provides insights for optimizing light and CO₂ to increase C. sorokiniana biomass and pigment yields for biotechnological applications.

The online version contains supplementary material available at 10.1007/s13205-025-04603-z.