Omega-3 fatty acids are essential in human nutrition
to ensure a well functioning of the metabolism and the cardiovascular system.
Two major forms of these fatty acids are EPA (eicosapentaenoic acid) and DHA
(docosahexaenoic acid). So far the main source of fish oils is the fish
industry itself. But with increasing environmental challenges on one hand and
economical and ethical issues on the other hand the production of fish oil is
facing some difficulties. Therefore scientists are looking into marine
microalgae as a potential and sustainable source for omega-3. A few research studies
were already conducted showing that microalgae provide a wide range of
advantages compared to fish stock but they mainly took place in southern latitudes,2.
The aim of this study was to evaluate the
suitability of microalgae as a source of EPA and DHA under northern climate
conditions on a large scale. The microalga of interest was the diatom Phaeodactylum tricornutum, a robust species
with some valuable characteristics, such as a high growth rate and high content
in EPA.
The study took place in Norway for a period of
six months categorized in three different seasons covering spring, summer and
autumn. As test subjects three strains of the diatom P. tricornutum were used, two local strains (M28 and B58) and one
commercial Spanish strain called Fito. The marine microalgae were cultivated in
big outdoor flat panel photobioreactors to enable the observation of strain
specific responses to the environmental characteristics. Each panel was observed
intensively regarding the pH, the temperature as well as the nitrate and
phosphate concentrations. The difficulty of the study consisted in maintaining
the conditions in the panel at a steady state. Due to some technical problems related
to the choice of equipment and methods the pH level fluctuated heavily at some
points of the experiment.
However the study lead to some interesting
findings. The highest biomass production with a correlating high content of EPA
was observed in the spring season because of the highest irradiance. The three
strains differed in their growth rate but weren’t consistent during all three
seasons. Compared to M28 and B58, Fito significantly showed the highest EPA
content.
The article showed that a cultivation of marine microalgae
on a large scale is possible in northern latitudes. However, this is efficient
only during half of the year, when the irradiance is high. This raises the
question if algal omega-3 is beneficial enough from an economical point of
view?
Even if the productivity of diatoms and the content
of EPA is stronger in southern located studies a big disadvantage is the cost
intensive cooling necessary because of the strong irradiance. In general the
cultivation of marine diatoms is still quite expensive compared to the
conventional fish industry. I think that a lot of improvements regarding the
methods and equipment will be needed. Another study showed that the acyl lipid
composition could be influenced by the age of the cells or by the use of
biolistic transformation2. Maybe this could be used in further
attempts to increase the EPA content in the diatoms. In my opinion improvements
regarding the experimental set-up could also have a great impact on the efficiency
of the study. The use of helical instead of flat panel photobioreactor1,
or even chemostats could be a way to enhance the stability of the cultures.
In sum, more research on this subject will be
needed even though the potential of marine microalga as a source of omega-3 is
undeniable.
Article
Reviewed
Steinrücken, P., Prestegard, S. K., de Vree, J. H.,
Storesund, J. E., Pree, B., Mjøs, S. A., & Erga, S. R. (2018). Comparing
EPA production and fatty acid profiles of three Phaeodactylum tricornutum
strains under western Norwegian climate conditions. Algal research, 30,
11-22.
References
1
Fernández, F. A., Hall, D. O., Guerrero, E. C., Rao, K. K., & Grima, E. M.
(2003). Outdoor production of Phaeodactylum tricornutum biomass in a helical
reactor. Journal of Biotechnology, 103(2), 137-152.
2 Alonso,
D. L., Belarbi, E. H., Fernández-Sevilla, J. M., Rodríguez-Ruiz, J., &
Grima, E. M. (2000). Acyl lipid composition variation related to culture age
and nitrogen concentration in continuous culture of the microalga Phaeodactylum
tricornutum. Phytochemistry, 54(5), 461-471.
3
Hamilton, M. L., Haslam, R. P., Napier, J. A., & Sayanova, O. (2014).
Metabolic engineering of Phaeodactylum tricornutum for the enhanced
accumulation of omega-3 long chain polyunsaturated fatty acids. Metabolic
engineering, 22, 3-9.
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information about the molecular method biolistic transformation:
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