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International Journal of Marine Science 2013, Vol.3, No.17, 135-144
http://ijms.sophiapublisher.com
141
related with cultivation condition including temperature,
nutrient limitation, CO
2
concentration and light
intensity (Lv et al., 2010). In this study we also
investigated the effect of different temperature and
nutrient conditions of media cultured on lipid content
using three different methods of lipid analysis, such as
Nile Red Staining, Gravimetric and FTIR spectroscopy.
3.2.1 Lipid analysis by Nile Red Fluorescence
Lipid content of three selected microalgae was
measured daily using Nile Red fluorescence method
(Figure 3). Figure 3 showed the total neutral lipid
content, as measured by Nile Red fluorescence, of
cultured subjected to these conditions. As shown, cell
Figure 3 Lipid concentration based on Nile Red Fluorescence
reading in response to varying nutrient and temperature
condition. Nile Red Fluorescence reading of (A)
Dunaliella
tertiolecta
, (B)
Scenedesmus
sp. and (C)
Nannochloropsis
sp.
cultured in -N medium cultured at 18
℃
and 25
℃
temperature cultivation condition contained a higher
amount of neutral lipid than in control and –P medium
for all algal cultured. The largest amount of neutral
lipid was recorded at day 9 and day 10 of cultivation
for
Scenedemus
sp.,
Dunaliella tertiolecta
and
Nannochloropsis
sp., respectively. The pattern of
neutral lipid content based on Nile Red fluorescence
reading of three selected microalgae were similar in
response to different temperature and nutrient
conditions. However,
Dunaliella tertiolecta
showed
the highest amount of neutral lipid for
-
N medium
treatment than
Scenedesmus
sp
.
and
Nannochloropsis
sp.
account for 0.210 potential fluorescence unit. Using our
Nile Red method we found that the cells grown under
nitrogen depletion condition exhibited 3 times, 2 times
and 1.5 times more fluorescence than cells grown under
nitrogen-sufficient conditions for
Dunaliella tertiolecta,
Scenedesmus
sp. and
Nannochloropsis
sp., respectively.
The fluorescence reading in this study was lower than
previous study by Elsey et al (2007) which recorded
6.7 times more fluorescence of cell grown under
nitrogen deficient condition than cells grown under
nitrogen-sufficient conditions. Low Nile Red fluorescence
reading for neutral lipid content in this study probably
due to no modification conducted to Nile Red assay.
Elsey et al (2007) reported that to improve ability of
screening for neutral lipids, either across multiple
microalgal strains grown under identical conditions, or
across varying growth conditions through conducting
modification to the Nile Red assay.
3.2.2 Lipid analysis by Gravimetric method
Figure 4 showed the relative neutral lipid content, as
measured by gravimetric method for different
temperature and nutrient conditions of three selected
microalgae. Lipid content was higher at
-
N medium
cultured than
-
P and sufficient nutrient treatments.
Culture with
-
P medium behaved similarly to culture
in
-
N medium at
Scenedesmus
sp. and
Nannochloropsis
sp. The result also indicated that temperature stress
increased lipid content for
Dunaliella tertiolecta
and
Scenedesmus
sp. (Figure 4A and 4B). Statistically,
there was a significant different of lipid content at –N
medium cultured between 18
℃
and 25
℃
(p<0.05).
Dunaliella tertiolecta
showed a higher lipid content at
–N medium cultured than
Scenedesmus
sp. and
Nannochloropsis
sp. account for 0.352 g/L. Lipid
accumulation under this condition appear as a response