Lipid accumulation and antioxidant activity in the eukaryotic acidophilic microalga Coccomyxa sp. (strain onubensis) under nutrient starvation

The chlorophtye Coccomyxa sp. (strain onubensis) growing under either inorganic phosphorus or sulfur starvation showed, unlike other non-extremophile microalgae, the ability to grow still for a period of 2 weeks with retention of high activity of photosystem II, due to P and S reserves in the microalga. Lutein and β-carotene contents slightly increased for a few days in nitrogen-lacking cultures only, with no major impact on productivity due to cease of growth. Maximum fatty acid content of Coccomyxa sp. (strain onubensis) growing in nutrient-lacking culture media accounted for about 13 % of dry biomass and about 50 % of the total lipid fraction, linolenic (C18:3) being the most abundant fatty acid. The lipid content of this microalga is on the average of non-extremophile microalgae, but it has the advantage of producing in highly acidic culture media (pH 2.5, and even lower) which allow its outdoor production-preserving cultures from other microalgae contamination. Nutrient-limited cultures showed a significant increase in the intracellular activity levels of the enzymes glutathione reductase (GR), ascorbate peroxidase (APX) and catalase (CAT), indicating a connection between nutrient deprivation and oxidative stress in Coccomyxa sp. (strain onubensis).