Nitrogen Deficiency Maximizes the Production and Accumulation of Β-Carotene via Induction of Different Macromolecule Derivatives in Dunaliella salina (Dunal) Teodoresco

Abstract

This study aims at investigating the effects of nitrogen deficiency and NaCl stress on β-carotene production and growth of Dunaliella salina (Dunal) Teodoresco. D. salina was exposed to different levels of N: 2.5, 4.9, 7.4 and 9.9 mM KNO3 or Na+: 1.3, 1.7, 2.6, 3.4 and 4.3 M NaCl. β-carotene production and accumulation were significantly better in nitrogen deficiency-treated D. salina than that in NaCl-treated cells, with a maximum increase of 5.5 mg g DW-1 at 2.5 mM KNO3. Algal growth, in terms of cell number and the relative growth rate (RGR), was increased with the increase in the availability of nitrogen but decreased by NaCl stress. In contrast, the production of β-carotene by D. salina was enhanced under nitrogen deficiency and excessive salinity, suggesting the opposite effect of nitrogen availability and stressful NaCl on the production and accumulation of β-carotene concomitant with the inhibition of algal growth. GC analysis confirmed that nitrogen deficiency-treated D. salina accumulates β-carotene higher than that in the outdoors-growing cells, suggesting the great potential of nitrogen deficiency-treated D. salina to produce different β-carotene macromolecule derivatives compared to those in the outdoors-growing cells. Such different hydrocarbons could be converted into safe β-carotene. Therefore, D. salina could be used as a reliable biological system for β-carotene production.