Chlorella sorokiniana has been selected for lutein production, after a screening
of thirteen species of microalgae, since it showed both a high content in this carotenoid and
a high growth rate. The effects of several nutritional and environmental factors on cell
growth and lutein accumulation have been studied. Maximal specific growth rate and lutein
content were attained at 690 μmol photons m−2 s−1, 28 °C, 2 mM NaCl, 40 mM nitrate and
under mixotrophic conditions. In general, optimal conditions for the growth of this strain
also lead to maximal lutein productivity. High lutein yielding mutants of C. sorokiniana
have been obtained by random mutagenesis, using N-methyl-N′-nitro-nitrosoguanidine
(MNNG) as a mutagen and selecting mutants by their resistance to the inhibitors of the
carotenogenic pathway nicotine and norflurazon. Among the mutants resistant to the
herbicides, those exhibiting both high content in lutein and high growth rate were chosen.
Several mutants exhibited higher contents in this carotenoid than the wild type, showing, in
addition, either a similar or higher growth rate than the latter strain. The mutant MR-16
exhibited a 2.0-fold higher volumetric lutein content than that of the wild type, attaining
values of 42.0 mg L−1 and mutants DMR-5 and DMR-8 attained a lutein cellular content of
7.0 mg g−1 dry weight. The high lutein yield exhibited by C. sorokiniana makes this
microalga an excellent candidate for the production of this commercially interesting pigment.