of pigment biosynthesis is a factor that might promote higher protein contents in this species. Moreover, because of their higher protein and lower chlorophyll contents, the MT01 and MT02 strains are likely candidates to be feedstocks for the development of novel, innovative food supplements and foods.

The industrial microalga Tetraselmis sp. CTP4 is a promising candidate for aquaculture feed, novel food, cosmeceutical and nutraceutical due to its balanced biochemical profile. To further upgrade its biomass value, carotenogenesis was investigated by testing four environmental factors, namely temperature, light intensity, salinity and nutrient availability over different growth stages. The most important factor for carotenoid induction in this species is a sufficient supply of nitrates leading to an exponential growth of the cells. Furthermore, high temperatures of over 30°C compared to lower temperatures (10 and 20°C) induced the accumulation of carotenoids in this species. Remarkably, the two different branches of carotenoid synthesis were regulated depending on different light intensities. Contents of β-carotene were 3-fold higher under low light intensities (33 μmol m −2 s −1 ) while lutein contents increased 1.5-fold under higher light intensities (170 and 280 μmol m −2 s −1 ). Nevertheless, highest contents of carotenoids (8.48 ± 0.47 mg g −1 DW) were found upon a thermal upshift from 20°C to 35°C after only two days at a light intensity of 170 μmol m −2 s −1 . Under these conditions, high contents of both lutein and β-carotene were reached accounting for 3.17 ± 0.18 and 3.21 ± 0.18 mg g −1 DW, respectively. This study indicates that Tetraselmis sp. CTP4 could be a sustainable source of lutein and β-carotene at locations where a robust, euryhaline, thermotolerant microalgal strain is required.

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In recent years, there has been increasing consumer interest on carotenoids particularly of marine sustainable origin with applications in the food, cosmeceutical, nutritional supplement and pharmaceutical industries. For instance, microalgae belonging to the genus Tetraselmis are known for their biotechnologically relevant carotenoid profile. The recently isolated marine microalgal strain Tetraselmis sp. CTP4 is a fast-growing, robust industrial strain, which has successfully been produced in 100-m 3 photobioreactors. However, there are no reports on total carotenoid contents from this strain belonging to T. striata/convolutae clade.Although, there are several reports on extraction methods targeting chlorophytes, extraction depends on the strength of cell coverings, solvent polarity and the nature of the targeted carotenoids. Therefore, this article evaluates different extraction methods targeting Tetraselmis sp. CTP4, a strain known to contain a mechanically resistant theca. Here, we propose a factorial experimental design to compare extraction of total carotenoids from wet and freeze-dried microalgal biomass using four different solvents (acetone, ethanol, methanol or tetrahydrofuran) in combination with two types of mechanical cell disruption (glass beads or dispersion). The extraction efficiency of the methods was assessed by pigment contents and profiles present in the extracts. Extraction of wet biomass by means of glass beadassisted cell disruption using tetrahydrofuran yielded the highest amounts of lutein and βcarotene (622 ± 40 and 618 ± 32 µg g -1 DW, respectively). Although acetone was slightly less efficient then tetrahydrofuran, it is preferable due to its lower costs and toxicity.