Effects of different abiotic stresses on carotenoid and fatty acid metabolism in the green microalga Dunaliella salina Y6

Abstract

Purpose: Under different abiotic-stress conditions, the unicellular green microalga Dunaliella salina accumulates large amounts of carotenoids which are accompanied by fatty acid biosynthesis. Carotenoids and fatty acids both possess long carbon backbones; however, the relationship between carotenoid and fatty acid metabolism is controversial and remains poorly understood in microalgae. Methods: In this study, we investigated the growth curves and the β-carotene, lutein, lipid, and fatty acid contents of D. salina Y6 grown under different abiotic-stress conditions, including high light, nitrogen depletion, and high salinity. Results: Both high-salinity and nitrogen-depleted conditions significantly inhibited cell growth. Nitrogen depletion significantly induced β-carotene accumulation, whereas lutein production was promoted by high light. The accumulation of lipids did not directly positive correlate with β-carotene and lutein accumulation under the three tested abiotic-stress conditions, and levels of only a few fatty acids were increased under specific conditions. Conclusion: Our data indicate that cellular β-carotene accumulation in D. salina Y6 positive correlates with accumulation of specific fatty acids (C16:0, C18:3n3, C14:0, and C15:0) rather than with total fatty acid content under different abiotic stress conditions.

Influence of Light Conditions on Microalgae Growth and Content of Lipids, Carotenoids, and Fatty Acid Composition

“…It is a known fact that the production of these carotenoids in Dunaliella salina increases with increasing light intensity. Thus, an increase in lighting from 100 to 200 µmol photons m −2 s −1 increased the accumulation of β-carotene in Dunaliella salina Y6 by 31.5% [79]. In other studies, Dunaliella strains (DF15, DF17, DF40, UTEX 253) demonstrated an increase in β-carotene productivity under lighting of more than 200 µmol photons m −2 s −1 and maximum productivity values (up to 3.5 mg L −1 day −1 ) were noted at 1500 µmol photons m −2 s −1 [48].…”

“…Algae grown under various light intensities show changes in biomass formation rate, pigment and lipid content, fatty acid composition, and ratio. For this purpose, various researchers have studied a fairly wide range of light intensity: from 5 to 3500 µmol photons m −2 s −1 [31,43,47,53,[77][78][79][80].…”

“…When the maximum rate of photosynthesis is reached, the excess light flux continues to be absorbed by the cell and this leads to a state of light saturation of photosynthesis. At the same time, there is a decrease in the rate of photosynthesis and algae growth [79,86,94,95].…”

“…In microalgae capable of both autotrophic and heterotrophic growth (for example, Haematococcus lacustris and Chromochloris zofingiensis, formerly known as Chlorella zofingiensis), heterotrophic conditions can significantly increase the productivity of biomass, but they cannot provide large amounts of pigments, including commercially valuable ones [120]. Exposure to high-intensity lighting increases carotenoid production in Haematococcus lacustris [37,121], Dunaliella salina [48,79], Chromochloris zofingiensis [122], Tetradesmus obliquus [123], Nostoc calcicola [124], etc. (Table 5).…”

Water reuse and growth inhibition mechanisms for cultivation of microalga Euglena gracilis

“…Samples of the microalgae were taken every other day to monitor the cells' dry weight (DW). DW was measured according to the method described by Wu et al [33]. Briefly, 5 mL microalgae suspension was filtered through a preheated (105 °C, 24 h), preweighed glass microfiber filter (Whatman GF/C, 47 mm, UK).…”