Effect of abiotic stress on the production of lutein and β-carotene by Chlamydomonas acidophila

Chlamydomonas acidophila growing autotrophically with continuous PAR light (160 μE m−2 s−1) and 30 °C may accumulate carotenoids which increase in response to abiotic stress, like high light intensity, UV-A radiation and temperature fluctuation. At PAR light of 240 μE m−2 s−1 the alga contains, after 20 days of growth, 57.5 ± 1.6 mg l−1 of total carotenoids, 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 zeaxanthin (0.2 ± 0.1 mg l−1) was low. Enhanced production of lutein and β-carotene were observed in the alga grown under standard conditions, but either supplemented with moderate UV-A radiation (10 μE m−2 s−1), or heated at 40 °C.The presence of Fe3+ in the culture medium, in a range between 5 and 35 mM, significantly decreased the C. acidophila viability and the intracellular carotenoids content. However Cu2+, at 1–5 mM, appears to increase the synthesis of β-carotene. The alga can grow under mixotrophic conditions, with glucose, 10 mM, as carbon source, but any of such conditions improved the intracellular content of carotenoids.