Pigment production by a new thermotolerant microalga Coelastrella sp. F50

Microalgae are good crops to produce natural pigments because of their high growth rates. Tropical zones are better locations than temperate areas for microalgal cultivation because they have longer duration of daylight and more stable temperatures throughout the year, but the high temperatures pose a challenge to microalgal cultivation. A newly isolated thermotolerant microalga produces reddish pigments under environmental stress. Morphological and molecular evidence including meridional ribs on the cell wall, pigment production, and its 18S rDNA sequence suggests that this microalga belongs to the genus Coelastrella. Salt stress and high light intensity accelerated biosynthesis of the pigments, and significant quantities of oil accumulated as the cells experienced stress due to nutrient deficiency. This microalga could withstand temperature of 50 °C for more than 8 h, which is a necessary trait for outdoor cultivation in tropical areas. The pigments contain astaxanthin, lutein, canthaxanthin, and β-carotene as analysed by using HPLC.