Abstract
Tisochrysis lutea is an important microalgal species for fucoxanthin and docosahexaenoic acid (DHA) production with an optimum cultivation temperature of approximately 30 °C. The aim of the present work was to develop a winter strain with high productivity at 15 °C. The response of the original strain to a decrease in temperature from 30 °C to 15 °C was investigated in continuous turbidostat experiments. This was followed by adaptation for >180 days at 15 °C and 2 rounds of sorting for cells with high chlorophyll fluorescence (top 5%) using fluorescence-activated cell sorting (FACS). For the original strain the productivity of biomass, fucoxanthin, and DHA decreased by 92 %, 98 % and 85 % respectively when decreasing the temperature from 30 °C to 15 °C. In the sorted cold-adapted ‘winter strain’, biomass, fucoxanthin, and DHA productivities were similar to those at 30 °C. In addition, the fucoxanthin concentration increased from 1.11 to 4.24 mg g−1 dry weight and the polar lipid fraction in total fatty acids increased from 21 % to 55 %. The winter strain showed a robust and stable phenotype after one year of cultivation, expanding the outdoor fucoxanthin and lipid production seasons for this species.
Highlights
Microalgae are among the most promising feedstocks for sustainable production of food, feed, materials, chemicals, and fuels [1,2,3,4,5]
The commercial application of microalgal biomass relies on large-scale cultivation and ideally strains can function in fluctuating light and temperatures
For the maintenance of the winter strains selected by fluorescence-activated cell sorting (FACS), cultures were inoculated in 100 mL Erlenmeyer flasks (SCHOTT AG, Mainz, Germany) with 50 mL medium, at 15 ◦C, light intensity ≈60 μmol m-2 s− 1, 18/6 h day/night cycle, and under constant agitation of 125 rpm
Summary
Microalgae are among the most promising feedstocks for sustainable production of food, feed, materials, chemicals, and fuels [1,2,3,4,5]. The commercial application of microalgal biomass relies on large-scale cultivation and ideally strains can function in fluctuating light and temperatures. For outdoor production without temperature control, microalgae will experience temperature fluctuations between 10 ◦C and 45 ◦C in temperate regions [6], including temperatures above the thresholds of survival of most commercialized microalgal species [7]. 30 ◦C, most microalgae cannot grow and active cooling is required. Most microalgal species are able to grow between 15 ◦C and 30 ◦C, with their optimal being between 20 ◦C and 25 ◦C [8]. The production location and season are limited, even in southern Europe where temperature fall below 20 ◦C during the winter [9]
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