Biomedical Engineering Reference
In-Depth Information
30
DHA 22:6(n-3)
25
EPA 20:5(n-3)
AA 20:4(n-6)
20
15
10
5
0
Figure 9.3
Average percentage compositions of the long chain polyunsaturated fatty acids (PUFAs)
docosahexaenoic acid (DHA; 22:6n-3), eicosapentaenoic acid (EPA; 20:5n-3) and arachidonic acid (AA;
20:4n-6) of different microalgal classes. Data compiled from over 40 species held in the Australian
National Algae Culture Collection.
high lipid contents include the green algal classes Euglenophyceae (e.g.
Euglena gracilis
),
Prasinophyceae (e.g.
Tetraselmis chui
and
T. suecica
) and the Eustigmatophyceae (e.g.
Nannochloropsis
spp.,), as well as members of the Prymnesiophyceae (e.g.
Pleurochrysis
carterae
and
Isochrysis galbana
) and Bacillariophyceae (diatoms) such as
Cyclotella
cryptica
.
Polyunsaturated fatty acids (PUFA) are essential dietary requirements for marine animals
and thus information on PUFA contents has been of considerable value to the aquaculture
industry. This work revealed significant compositional differences between algal classes
(Figure 9.3) and illustrated the ability to manipulate relative proportions of desired fatty
acids by changes to the growth conditions (Dunstan
et al
., 1993 ). Unusual fatty acids have
been identified, including C
28
polyunsaturated fatty acids in dinoflagellates (Mansour
et al
.,
1999), indicating that there is still much to be learned about the biosynthetic pathways for
fatty acid synthesis in marine microalgae.
Commercial production of microalgae for their high fatty acid content has now been
achieved by a number of companies. For example, early work by Martek Biosciences
identified a dinoflagellate
Crypthecodinium cohnii
that produces a high content of
docosahexaenoic acid (22:6n-3, DHA), which plays a key role in infant development and
adult health. While DHA is usually thought of as a fish oil constituent, it is also the most
abundant omega-3 fatty acid in the human brain and retina. Martek patented a method of
deriving DHA-rich oil from the alga which contains 40-50% DHA, but no eicosapentaenoic
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