Exposure to different light and temperature regimes reveals high plasticity in Galdieria cultures

This study explores the growth performance, macromolecular composition, and pigment production of the thermoacidophilic microalga Galdieria yellowstonensis CCMEE 5587.1 under diverse cultivation conditions relevant to large-scale applications. The effects of constant temperatures (30–50 °C), light intensities (0–400 μmol m −2 s −1 ), and temperature fluctuations (30–45-30 °C and 35–50-35 °C) combined with photoperiod regimes (24:0 h and 12:12 h) were systematically assessed in mixotrophic cultures using 10 g L −1 of glucose under a C/N ratio of 5. G. yellowstonensis exhibited remarkable adaptability, achieving a biomass productivity of 1.72 g L −1 d −1 and a maximum cell concentration of 10.65 g L −1 at a light intensity of 200 μmol m −2 s −1 . The strain exhibited optimal growth at constant temperatures of 35, 40, 42, and 45 °C. Even under extreme temperature fluctuations (35–50–35 °C), the alga maintained consistent growth rates, with no effects from photoperiod changes. Macromolecular composition, including protein, lipids, carbohydrate, and pigment content, demonstrated resilience to environmental variability, while phycocyanin productivity peaked (80 mg L −1 d −1 ) at moderate light intensity (200 μmol m −2 s −1 ). These findings underscore the high metabolic flexibility of G. yellowstonensis , reinforcing its potential for biotechnological applications in high-temperature environments. • G. sulphuraria showed optimal growth between 35 and 45 °C. • No growth occurred at a constant temperature of 50 °C. • Daily 3-h peaks at 50 °C did not inhibit growth of G. sulphuraria . • No photoinhibition occurred at light intensities up to 400 μmol m −2 s −1 . • Photoperiod did not affect mixotrophic growth or biomass composition.