Studying the effect of
different irradiances of light
on the triacylglycerol yield
in the marine diatom
Thalassiosira pseudonana
Megan Snyder and Sam Huynh
Background Information

T. pseudonana is classified as phytoplankton
(photosynthesizing marine organisms)
◦ Diatom (microscopic, unicellular, photosynthetic
algae with a silica shell called a frustule)
Bacillariophyceae class (largest group of biomass
producers)100,000+ species
 High oil content (21-31%) by dry weight
 Entire genome is sequenced
 Oil helps it float on the water to
photosynthesize

http://www.diark.org/img/species_pict/T
halassiosira_pseudonana_CCMP1335
Oil from diatom is a potential alternative fuel
 Oil composed of lipids

◦ Lipid: biological compound insoluble in water but
soluble in organic solvents
Triacylglycerol (specific lipid) acts primarily as
energy storage in diatoms (three fatty acids
attached to one glycerol)
 Triaclyglcerol is a non-polar, or neutral lipid

◦ Polar lipids have a hydrophilic and a hydrophobic end;
neutrals do not.
◦ Polar lipids located in cell walls

Triacylglycerol Transesterification

process to refine triacylglycerol; how does it become
biodiesel?

Oil is purified and reacted with methanol or ethanol in the
presence of a catalyst (such as KOH potassium hydroxide or
NaOH sodium hydroxide); the triacylglycerol is transformed to
form esters and glycerol – remaining esters are biodiesel
Triacylglycerol Chemical Formula
http://www.oliveoilsource.com/page/chem
ical-characteristics
Glycerol
3 Fatty Acids

Nile red (9-diethylamino-5Hbenzo[α]phenoxazine-5-one) is a dye that
collects in the neutral lipids of living cells
◦ Fluoresces under a certain wavelength, then emits
another wavelength
◦ The intensity of the fluorescence is directly
correlated to lipid content
Purpose: increase the triacylglycerol content in
the diatom using different light irradiances
 Importance: increased triacylglycerol yields per
diatom can make the process of making bio-fuel
from algae more efficient and economically
feasible

Irradiance: measure of light that reaches
the product surface
 Why measure in irradiance and not
intensity? Photosynthesis depends on the
amount of light reaching the surface of
the plant, not the intensity of the source

Procedure

Diatoms will grow a plastic container under
different irradiances of fluorescent light (test
one irradiance at a time)
◦ Sides of the container will be covered with aluminum
foil to block out excess light
◦ In previous experiments, irradiances of light have
affected photosynthetic processes in T. pseudonana
◦ Light on a 16 hour-on, 8 hour-off cycle, maintained by
a light timer
Grown in f/2 agar, a solution that provides
nutrients for marine algae
 pH measured periodically with a Vernier probe
to make sure CO2 levels stay constant
 Container inside Styrofoam box with ice packs
to keep temperature constant at about 53°F
 Nile red stain will be applied to a few sample
diatoms after six days

Data Collection

Use UV microscope equipped with a camera
◦ Takes pictures of the cells fluorescing

Use Image J program to analyze level of
fluorescence
Green Algae
stained with
Nile redTriacylglycerol
fluoresces
yellow-gold,
phospholipids
fluoresce red
Inverted UV
microscope
http://www.chemistrytimes.com/Images/g
reen_alga_with_nile_red.jpg
http://accu-scope.net/3032_EPI_318CU.gif
Bibliography
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Chemical Education Digital Library (2007 a). Polar Lipids. Retrieved from:
http://chemed.chem.wisc.edu/chempaths/GenChem-Textbook/Polar-Lipids-1019.html
Chemical Education Digital Library (2007 b). Nonpolar Lipids. Retrieved from:
http://chemed.chem.wisc.edu/chempaths/GenChem-Textbook/Nonpolar-Lipids-1018.html
Chen, W., Zhang, C., Song, L., Sommerfield, M., & Hu, Q. (2009). A high throughput Nile red
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chlorophyll A ratios of Thalassiosira pseudonana (bacillariophyceae) cultured under different
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http://www.3rd1000.com/chem301/chem302p.htm
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http://science.howstuffworks.com/environmental/green-science/algae-biodiesel2.htm
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http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/lipids.htm#lipid1
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