Abstract
PurposeUnder 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.MethodsIn 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.ResultsBoth 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.ConclusionOur 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.
Highlights
Carotenoids are naturally occurring yellow- to orangered-colored compounds with a polyisoprene backbone, mainly comprising β-carotene and lutein, which are found in bacteria, cyanobacteria, microalgae, fungi, and plants (Concepcion et al 2018; Kanzy et al 2015; Saini and Keum 2017)
We investigated the growth curves and the β-carotene, lutein, lipid, and fatty acid contents of the green microalga D. salina Y6 under high light (HL), nitrogen depletion (ND), and high salt (HS) conditions in order to investigate the relationship between carotenoid production and fatty acid metabolism in this species
DW and cellular content of HL-treated cells were lower than those of the control (p < 0.05) (Fig. 2). These results indicate that HL promotes D. salina Y6 culture growth but inhibits the accumulation of cellular biomass
Summary
Carotenoids are naturally occurring yellow- to orangered-colored compounds with a polyisoprene backbone, mainly comprising β-carotene and lutein, which are found in bacteria, cyanobacteria, microalgae, fungi, and plants (Concepcion et al 2018; Kanzy et al 2015; Saini and Keum 2017). The unicellular green microalga Dunaliella salina (Chlorophyta) is rich in β-carotene, which accumulates at approximately 5–10 mg/L dry weight under suitable growth conditions, similar to other higher plants, fungi, and bacteria (Ku et al 2019; Miller et al 2013; Yen et al 2019). The amount of carotenoids produced in microalgal D. salina (CCAP 19/18) cells is positively correlated with the synthesis of fatty acids oleic acid (C18:1) and palmitic acid (C16:0), and has little association with lipids under HL and ND conditions (Lamers et al 2010; Mendoza et al 1999). The relationship between carotenoid and fatty acid metabolism is controversial and remains to be elucidated in microalgae
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