Chlamydomonas acidophila growing autotrophically with continuous PAR light (160 µE.m-2.s-1) and 30 ºC may accumulate carotenoids which increase in response to abiotic stress, like high light intensity, UV-A radiation and temperature fluctuation. At 240 µE.m-2.s-1 the alga contains 57.5 ± 1.6 mg.l-1 of total carotenoids after 20 days of growing, which does not significantly change by an irradiance of 1000 µE.m-2.s-1. Lutein (20 ± 0.5 mg.l-1) and β-carotene (8.3 ± 0.2 mg.l-1) production were particularly high in C. acidophila, while zeaxanthine (0.2 ± 0.1 mg.l-1) was low. Enhanced production of these carotenoids was also observed in cultures illuminated with PAR light (160 µE.m-2.s-1) supplemented with moderate UV-A radiation (10 µE.m-2.s-1).
Optimum algae growth takes place at 40 ºC, like the maximum amount of intracellular lutein and β-carotene. On the other hand, the presence of iron in the culture medium, in a range between 5-35 mM, significantly decreased the cell viability and the intracellular content of carotenoids, however cupper, at 1-5 mM, appears to increase the synthesis of β-carotene. The alga can growth under mixotrophic conditions, with glucose or acetate, 10 mM, as carbon source, but such conditions did not improved the intracellular content of carotenoids
