Characteristics of a New Halotolerant Arctic Strain of Carotenogenic Microalga Halochlorella rubescens NAMSU SBB-20

Green microalgae capable of accumulating secondary carotenoids are the most important objects of biotechnology, and the search for new strains with unique properties, in particular, those adapted to growth at low temperatures and high salinity in the environment, is an urgent task. The NAMSU SBB-20 microalga strain was isolated from an algal-bacterial biofilm found on the coast of the White Sea in the littoral zone of the Solovetsky Archipelago. Identification of the strain showed its belonging to the species Halochlorella rubescens P.J.L.Dangeard. The species H. rubescens was first described for the White Sea. Under conditions of high light intensity, ultrastructural changes in cells are shown, among which destruction of the photosynthetic apparatus and the formation of cytoplasmic and chloroplast lipid inclusions are noted. It was shown that the culture of the NAMSU SBB-20 strain is capable of acquiring an orange color under unfavorable growth conditions. An assessment was made of the effect of the composition of the medium and the intensity of illumination on the pigment composition of the algae. The highest absolute values of the accumulation of carotenoids were noted during cultivation in light with an intensity of 150 μmol PAR quanta/m2/s on BG-11 media containing no source of phosphorus (15.66 ± 0.18 mg/L) or nitrogen (15.95 ± 0.56 mg/L). The described strain has a biotechnological potential due to the initial halotolerance and the accumulation of high values of secondary carotenoids in the biomass.