ИСТИНА

Green unicellular algae from the genus Dunaliella are the main or even sole primary producers in environments with salinity close to saturation and represent an important source of β-carotene. In Russia there are a lot of hypersaline lakes which can be used as resource of new strains of these valuable microalgae. Phylogenetic position of nine Dunaliella isolates from Salt-Iletsk' Lakes in Orenburg region and Elton Lake in Volgograd region was studied based on the ITS1–5.8S rRNA–ITS2 sequence. The capability of accumulation of secondary (uncoupled from the photosynthetic apparatus) β-carotene in five novel strains of halophile microalga from the genus Dunaliella was analyzed in condition of high photosynthetically active radiation and nirogen deficiency. The growth rate, pigment and fatty acids content and composition as well as suspension absorbance spectra were investigated in microalgae cultures under optimal and stress conditions. Under conditions optimal for growth, chlorophylls and primary carotenoids (mainly lutein) dominated in the pigment profile of all investigated strains. The main fatty acids were represented by unsaturated C18 FA typical of thylakoid membrane structural lipids. In all studied cells, stressors caused a decline in chlorophylls and an increase in saturated C16 and C18 FA associated with reserve lipids. Fatty acid saturation increased (apparently due to net loss of lipids associated with thylakoid membranes).The carotenogenic species D. salina demonstrated 10-fold increase in carotenoids accompanied by a decline in lutein and a drastic increase in β-carotene (up to 75% of total carotenoids). In D. parva and D. viridis, only 1.5-fold increase in carotenoid content took place, the ratio of major carotenoids remaining essentially unchanged. Funding by the Russian Scientific Found is greatly appreciated (project No. 14-50-00029).