Production of lutein, and polyunsaturated fatty acids by the acidophilic eukaryotic microalga Coccomyxa onubensis under abiotic stress by salt or ultraviolet light

Abstract

In this study, the effect of abiotic stress on the acidophilic eukaryotic microalga, Coccomyxa onubensis, was analyzed for the production of lutein and PUFAs (polyunsaturated fatty acids). It grows autotrophically at a pH of 2.5. It showed a growth rate of 0.30 d^-1, and produced approximately 122.50 mg·L^-1·d^-1 biomass, containing lipids (300.39 mg g^-1dw), lutein (5.30 mg g^-1dw), and β-carotene (1.20 mg g^-1dw). The fatty acid methyl ester (FAME) fraction was 89.70 mg g^-1dw with abundant palmitic acid (28.70%) and linoleic acid (37.80%). The addition of 100 mM NaCl improved the growth rate (0.54 d^-1), biomass productivity (243.75 mg·L^-1·d^-1), and lipids accumulation (416.16 mg g^-1dw). The microalga showed a lutein content of 6.70 mg g^-1dw and FAME fraction of 118.90 mg g^-1dw; 68% of the FAMEs were PUFAs. However, when 200-500 mM salt was added, its growth was inhibited but there was a significant induction of lutein (up to 7.80 mg g^-1dw). Under continuous illumination with PAR (photosynthetically active radiations) +UVA (ultraviolet A, 8.7 W m^-2), C. onubensis showed a growth rate of 0.40 d^-1, and produced 226.3 mg·L^-1·d^-1 biomass, containing lipids, (487.26 mg g^-1dw), lutein (7.07 mg g^-1dw), and FAMEs (232.9 mg g^-1dw); 48.4% of the FAME were PUFAs. The illumination with PAR + UVB (ultraviolet B, 0.16 W m^-2) was toxic for cells. These results indicate that C. onubensis biomass is suitable as a supplement for functional foods and/or source of high added value products.

Keywords: Abiotic stress; Antioxidant enzymes; Coccomyxa onubensis; Fatty acid profile; Lipid accumulation; Lutein.