Abstract
Microalgae are excellent sources of polyunsaturated fatty acids (PUFAs), but only a few species have been thoroughly investigated in controlled photobioreactor conditions. In this work, the cold-adapted microalga Koliella antarctica (Trebouxiophyceae) was cultivated at 15 °C to optimize growth and PUFA production in bubble-tube and flat-plate photobioreactors. The impact of nitrogen starvation, phosphorus starvation, salinity, and light intensity on the growth, fatty acid, and protein content was investigated. After culture optimization, a maximum biomass productivity of 2.37 g L−1 day−1 and maximum cell density of 11.68 g L−1 were achieved. Among all conditions tested, the maximum total fatty acid (TFA) content measured 271.9 mg g−1 dry weight in the late stationary phase. Nitrogen and phosphorus starvation strongly induced neutral lipid (TAG) accumulation, up to 90.3% of TFA, which mostly consisted of the monounsaturated fatty acid C18:1n−9 (oleic acid, OA). PUFAs were also abundant and together accounted for 30.3–45.8% of total triacylglycerol (TAG). The highest eicosapentaenoic acid (EPA) content (C20:5n−3) amounted to 6.7 mg g−1 dry weight (4.9% TFA) in control treatments, while the highest arachidonic acid (ARA) content (C20:4n−6) was 9.6 mg g−1 dry weight (3.5% TFA) in the late stationary phase. Phosphorus starvation was an effective strategy to obtain high total fatty acid yields (mg L−1) while maintaining the protein, total PUFA, and omega-3 fatty acid contents.
Highlights
Microalgae are excellent sources of bioactive compounds that are known to benefit animal and human health (Borowitzka 2013)
The growth of K. antarctica in different salinities ranging from freshwater (0‰) to seawater (32‰) conditions is shown in Table 2 and Fig. 1S
At salinity levels from 0 to 16‰, the maximum dry weight was in the range 2.69 to 2.90 g L−1
Summary
Microalgae are excellent sources of bioactive compounds that are known to benefit animal and human health (Borowitzka 2013). Cold-adapted microalgae from polar habitats recently gained attention for PUFA production (Teoh et al 2004; Spijkerman et al 2012; Artamonova et al 2017) and for their potential to achieve relatively high productivity at lower water temperatures (Hulatt et al 2017) Their evolutionary adaptations have enabled them to successfully colonize many low-temperature areas, including glaciers, sea ice, and polar and alpine regions, which are often characterized by large seasonal fluctuations in environmental factors such as light and osmotic stress (Morgan-Kiss et al 2006; Procházková et al 2018). Cold-adapted microalgae might be more productive sources of PUFAs and other algae derivatives that could be used in food or feed products
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