Effects of sustained trace element nutrient stress on biomass, bioactive compounds, lipidomics and nutritional and antioxidant properties of Dunaliella salina

This study investigates the effects of sustained nutrient stress caused by reduced concentrations of trace elements (Fe, Mn, Zn, Cu, Co, Mo at 25%, 50% and 75% of standard levels in Guillard’s f/2 medium) on the biomass and nutritional and antioxidant properties of the unicellular green alga Dunaliella salina. Over a 12-day cultivation period under controlled photoautotrophic conditions, significant variations were observed. Biomass productivity remained stable in the control (p > 0.05) and at 75% trace element levels. β-carotene synthesis peaked at 1.90 mg g‒1 day‒1 in Mn 50% compared to other treatments (p < 0.05). Lipid content reached a maximum of 58.78% in Fe 25%, significantly higher than in other treatments (p < 0.05), with triacylglycerol (TAG) content increasing to 68.1% in Fe 50% (p < 0.05), indicating enhanced lipid accumulation under 50% iron limitation. Fatty acid profiles revealed elevated C16:1 and C18:1 in Fe 75% (p < 0.05), while Co 75% exhibited the highest C18:2n6cis (6.82 ± 0.32%) (p < 0.05). Antioxidant activity peaked at 97.09% in Fe 25% at 40 mg ml‒1 of DPPH radical scavenging (p < 0.05), with a strong correlation (r = 0.974–0.986, p < 0.001) between β-carotene content and antioxidant capacity. Bioactive compounds, including lutein (2.05 µg mg‒1) and phenolics (4.05 mg GAE g‒1) in Fe 25% (p < 0.05), and trace element uptake patterns further elucidated nutrient dynamics. Principal component analysis (PCA) of all variance explained 81.0% of variance, linking PC1 to bioproduct yields and PC2 to trace element retention. These findings demonstrate that reduced trace element levels (25–50%) optimize lipid, β-carotene and antioxidant yields, offering a viable strategy for enhancing the biotechnological potential of D. salina for biofuel, nutraceutical and bioremediation applications.