Abstract
Long chain polyunsaturated fatty acids (LC-PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are considered essential omega-3 fatty acids in human nutrition. In marine microalgae EPA and/or DHA are allegedly involved in the regulation of membrane fluidity and thylakoid membrane functioning. The cellular content of EPA and DHA may therefore be enhanced at low temperature and irradiance conditions. As a result, polar and cold temperate marine microalgal species might potentially be suitable candidates for commercial EPA and DHA production, given their adaptation to low temperature and irradiance habitats.In the present study we investigated inter- and intraspecific EPA and DHA variability in five polar and (cold) temperate microalgae. Intraspecific EPA and DHA content did not vary significantly in an Antarctic (Chaetoceros brevis) and a temperate (Thalassiosira weissflogii) centric diatom after acclimation to a range of irradiance levels at two temperatures. Interspecific variability was investigated for two Antarctic (Chaetoceros brevis and Pyramimonas sp. (Prasinophyceae)) and three cold-temperate species (Thalassiosira weissflogii, Emiliania huxleyi (Prymnesiophyceae) and Fibrocapsa japonica (Raphidophyceae)) during exponential growth. Interspecific variability was shown to be much more important than intraspecific variability. Highest relative and absolute levels of DHA were measured in the prymnesiophyte E. huxleyi and the prasinophyte Pyramimonas sp., while levels of EPA were high in the raphidophyte F. japonica and the diatoms C. brevis and T. weissflogii. Yet, no significant differences in LC-PUFA content were found between polar and cold-temperate species. Also, EPA and DHA production rates varied strongly between species. Highest EPA production rate (174 μg L-1 day-1) was found in the Antarctic diatom Chaetoceros brevis, while DHA production was highest in the cold-temperate prymnesiophyte Emiliania huxleyi (164 μg L-1 day-1). We show that, following careful species selection, effective mass cultivation of marine microalgae for EPA and DHA production may be possible under low temperature and irradiance conditions.
Highlights
Marine microalgae are key organisms in the production of long chain polyunsaturated fatty acids (LC-PUFAs) in marine food webs (Harwood and Jones 1989; Guschina and Harwood 2006)
Highest relative and absolute levels of docosahexaenoic acid (DHA) were measured in the prymnesiophyte E. huxleyi and the prasinophyte Pyramimonas sp., while levels of eicosapentaenoic acid (EPA) were high in the raphidophyte F. japonica and the diatoms C. brevis and T. weissflogii
In this study we focused on EPA and DHA content and productivity in polar and temperate marine microalgae with an eye towards future high-latitude mass cultivation
Summary
Marine microalgae are key organisms in the production of long chain (between 14 and 22 carbon atoms) polyunsaturated fatty acids (LC-PUFAs) in marine food webs (Harwood and Jones 1989; Guschina and Harwood 2006). EPA and DHA are considered essential elements in human nutrition. EPA and/or DHA function as hormone precursors and are thought to play a role in the immune system (Calder 1997; Uauy et al 2000). Microalgae are the primary producers of EPA and DHA in marine food webs, until now their principal source for human nutrition is marine fish oil (Sinclair 2000). The production costs of DHA or EPA from cultured algae is potentially equal to the cost of producing EPA from fish oil (Milledge 2011). The efficiency should be further increased by selecting EPA- and/or DHA-rich species while at the same time optimizing mass cultivation and harvest conditions
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