Enhancing EPA Content in an Arctic Diatom: A Factorial Design Study to Evaluate Interactive Effects of Growth Factors

Abstract

Microalgae with a high content of the omega-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) are of great demand for microalgae-based technologies. An Arctic strain of the diatom Attheya septentrionalis was shown in previous experiments to increase its EPA content from 3.0 to 4.6% of dry weight (DW) in the nutrient-replete exponential phase and nutrient-depleted stationary phase, respectively. In the present study, a factorial-design experiment was used, to investigate this effect in more detail and in combination with varying salinities and irradiances. A mathematical model revealed that both growth phase and salinity, alone and in combination, influenced the EPA content significantly. Maximum EPA values of 7.1% DW were obtained at a salinity of 22 and after 5 days in stationary phase, and might be related to a decreased silica content, an accumulation of storage lipids containing EPA, or both. However, growth rates were lower for low salinity (0.54 and 0.57 d−1) than high salinity (0.77 and 0.98 d−1) cultures.

Variation in the fatty acid profiles of two cold water diatoms grown under different temperature, light, and nutrient regimes

“…The amount of EPA at 3% of AFDW was comparable to the best values obtained with P. tricornutum (Jiang and Gao 2004). Thalassiosira baltica had a higher share of EPA than comparable cold water diatoms (Artamonova et al 2017;Steinrücken et al 2017Steinrücken et al , 2018Peltomaa et al 2019), with the exception of Porosira glacialis that provides up to 10% S2 EPA of total FAs (Svenning et al 2019). Thalassiosira baltica could thus be a good candidate species for EPA production in a brackish, cold water cultivation system.…”

“…Using DW creates a bias when comparing diatoms with other algal groups and when comparing different diatoms because some species are more silicified than others. Even within the same species, the degree of silicification may differ, e.g., due to Si-limitation, which may shift the FA content per DW unit when the ash content decreases (Steinrücken et al 2018).…”

Microalgae biotechnology in Nordic countries – the potential of local strains

“…Moreover, outdoor vs indoor (laboratory) cultivation had a profound effect on the fatty acid composition. The arctic strain of Attheya septentrionalis was grown in a factorial design experiment in which growth phase, salinity and irradiance were applied in different combinations to reveal the effect on EPA production (Steinrücken et al ). The highest EPA content (7% of dry weight) was obtained at lower salinity of the growth media (salinity of 22) and after 5 days in stationary phase.…”

Recent Progress on Systems and Synthetic Biology of Diatoms for Improving Algal Productivity

“…Abiotic stresses, such as light, salinity, pH, and temperature stress, can increase the content of metabolites but reduce the biomass productivity of diatoms, leading to a decrease in overall yield. For example, under low salinity conditions, the EPA content in the arctic diatom Attheya septentrinalis increased, while its growth rate dropped significantly compared with that under the natural seawater condition (Steinrücken et al, 2018). In addition, the lipid content in P. tricornutum increased under high pH stress, while its carotenoid content increased under low pH stress, although their growth rates decreased under both pH stress conditions (Mus et al, 2013).…”