Biomedical Engineering Reference
In-Depth Information
Table 1 Biomass productivity, lipid content and lipid productivity of 30 microalgal strains
cultivated in 250-mL flasks (adapted from [
14
])
Microalgae
Biomass productivity
(mg L
-1
d
-1
)
Lipid content
(%)
Lipid productivity
(mg L
-1
d
-1
)
Nannochloropsis sp. RM
278.8 ± 0.0
31.0 ± 0.5
86.3 ± 0.0
Nannochloropsis sp. RP
232.7 ± 25.7
37.0 ± 0.5
86.1 ± 9.5
Nannochloropsis sp. ZM
241.8 ± 7.7
33.1 ± 1.7
79.9 ± 2.6
Pavlova lutheri
212.5 ± 10.6
37.1 ± 0.5
78.9 ± 3.9
Scenedesmus sp. DM
348.2 ± 2.6
21.8 ± 0.6
75.8 ± 0.6
Pavlova salina
240.0 ± 7.1
31.1 ± 1.4
74.6 ± 2.2
Chlorocomccum sp. UMACC 112
380.0 ± 2.6
19.5 ± 0.7
74.2 ± 0.5
Nannochloropsis sp. CS 246
231.8 ± 1.3
30.4 ± 0.3
70.4 ± 0.4
Nannochloropsis sp. MRS
270.0 ± 2.6
24.9 ± 0.7
67.2 ± 0.6
Ellipsoidium sp. LW 70/01
235.5 ± 1.3
28.4 ± 0.4
67.0 ± 0.4
Based on these criteria, one strategy for choosing and establishing model
oleaginous microalgae starts with the present laboratory microalgae. It takes
advantage of the abundant genomics resources and widely accessible genetic
systems that are typically found in these microalgae. However, this approach
suffers from several drawbacks, in that existing laboratory organisms are of low oil
productivity; for example, C. reinhardtii [
13
] accumulate only 2% of triacyl-
glycerol under nutrient starvation conditions. A potentially even bigger challenge
is that after numerous generations of laboratory propagations, these laboratory
strains could have largely lost the environmental tolerance that allows robust
growth under large-scale (typically outdoor and open-pond) cultivation. The other
strategy, instead, starts with wild microalgal strains that are able to synthesize and
accumulate large amounts of lipids under large-scale cultivation, such as certain
Nannochloropsis and Chlorella strains.
4 Advantages of Nannochloropsis
Nannochloropsis (Eustigmatophyceae) is a genus of unicellular photosynthetic
microalgae, ranging in size from 2 to 5 lm and widely distributed in marine, fresh
and brackish waters. In several pioneering large-scale outdoor cultivation facili-
ties, Nannochloropsis strains such as N. salina and N. oceanica have demonstrated
(Table
1
) (1) rapid and robust growth, including when supplied with flue gases, (2)
ability to accumulate high levels of triacylglycerols naturally or upon induction at
a demonstration scale [
14
], and (3) exceptional tolerance to environmental stres-
ses. Moreover, they are able to abundantly build up pigments such as astaxanthin,
zeaxanthin and canthaxanthin and to accumulate high levels of polyunsaturated
fatty acids (e.g. eicosapentaenoic acid, EPA) [
15
-
17
]. On the other hand, emerging
genomics data on eight Nannochloropsis strains that represent every known spe-
cies in the genus suggest that Nannochloropsis strains feature small genome sizes,
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