Nannochloropsis, a green microalga, is source for commercially valuable compounds as
extensively described and, in particular, is recognized as a good potential source of EPA
(20:5v3), an important polyunsaturated fatty acid for human consumption for prevention
of several diseases. Climate change might include variation in the UV levels, as one of
the consequences derived from the antropogenic activity. This paper shows the response
of Nannochloropsis cultures exposed for 7 days to UV-A added to PAR. Growth rates
and photosynthetic activity were assessed to determine the impact of UV-A increased
levels on the cell growth and basic metabolism activity. Xanthophyll pigments
(zeaxanthin and violaxanthin), carotenoids (cantaxanthin and β-carotene) and PUFAs
(miristic, palmitic, palmitoleic, araquidonic and eicosapentanoic acids) were measured
for assessing the antioxidant response of the microalgae to added UV-A radiation to
PAR. The results show that the modulated use of UV-A radiations can led to increased
growth rates which are sustained in time by an increased light transduction activity. The
expected antioxidant response to the incident UV-A radiation consisted of increases in
zeaxanthin and β-carotene contents –synthesis of antioxidant carotenoids- and increases
in the SFAs (saturated fatty acids) to PUFAs (polyunsaturated fatty acids) ratio. The
results suggest that modulated UV-A radiation can be used as a tool to stimulate value
molecules accumulation in microalgae through an enhanced both light transduction
process and antioxidant response, while sustaining cell growth
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