| Table 1 – Manipulation of environmental conditions and genetic engineering attempts to increase lipid production and biomass accumulation in diatoms.
EASW, enhanced artificial sea water; PUFA, polyunsaturated fatty acids; MUFA, monounsaturated fatty acids; SFA, saturated fatty acids; TFA, total fatty acids.
Diatom
|
Stress conditions / transformation / mutagen
|
Growth conditions
|
Growth rates
(day -1)
|
Physiological changes
|
Reference
|
Nitrogen limitation/starvation
|
Phaeodactylum tricornutum UTEX640
(Marine)
|
Nitrogen limitation (From 2 to 10 mM)
|
Fermenter, EASW, 1200 μmol photons m2 s-1, 20 °C
|
0 .29-0.57
|
Total lipids were 11% of the dry weight.
For cultures grown at 0.29 d-1, the lipid content increased to 19% upon nitrogen starvation.
TAG levels increased from 69 to 75% of the total lipid content with nitrogen limitation.
|
[1]
|
Phaeodactylum tricornutum
|
Nitrogen starvation
|
ASW based F/2, 300 μmol photons m2 s-1 white fluorescent, continuous light, 18 °C
|
0.97 (+N);
0.21 [2]
|
TFA increased by 76%, from 2.39 to 4.21 pg cell-1
Quantum requirement for incorporating FA, increased by 216%
|
[3]
|
Phaeodactylum tricornutum
|
Nitrogen starvation
|
ASW based F/2, 200 μmol photons m2 s-1 white LED, continuous light, 18 °C
|
0.86 (+N);
0.31 [2]
|
TFA increased by 21%, from 2.9 to 3.5 pg cell-1
Quantum requirement for incorporating FA, increased by 155%
|
[4]
|
Thalassiosira pseudonana (CCMP 1335)
(Marine)
|
Nitrogen starvation
|
Natural seawater, 210 μmol photons m2 s-1 12:12h L:D, 19 °C.
|
1.21 (+N);
0 [2]
|
Lipid content increased from 13% to 20% of the dry weight
|
[5]
|
Chaetoceros muelleri (Schütt)
(Marine)
|
Nitrogen starvation
|
SERI Types I and II media, 150 μmol photons m2 s-1, 5 - 45 °C.
|
Growth rates average ~1.5 d-1 and reached as high as 3.5 d-1 at high temperature (30 °C) under N replete conditions
|
Total lipid content increased by 7-folds after nitrogen starvation.
|
[6]
|
Navicula pelliculosa
(Freshwater)
|
Nitrogen starvation (7-9 days)
|
WC medium 23 °C, 190 µmol photons m-2 s-1
|
1.1 (during exponential phase)
|
Total lipids content reached 44.8% of the cell’s dry weigh.
|
[7]
|
Nitzschia palea
(Freshwater)
|
Nitrogen starvation
(7-9 days)
|
WC medium 23 °C, 190 µmol photons m-2 s-1
|
3.8 (during exponential phase)
|
Total lipids content increased from 22 to 40% of the cell’s dry weight.
|
[7]
|
Cyclotella cryptica
(Marine)
|
Nitrogen starvation
(7-9 days)
|
F/2 medium 23 °C, 190 µmol photons m-2 s-1
|
2.6 (during exponential phase)
|
Total lipids content increased from 23 to 37% of the cell’s dry weight.
|
[7]
|
Skeletonema costatum
(Marine)
|
Nitrogen starvation
(7-9 days)
|
F/2 medium 23 °C, 190 µmol photons m-2 s-1
|
2.7 (during exponential phase)
|
Total lipids content increased from 24 to 30% of the cell’s dry weight.
|
[7]
|
Silicates limitation/starvation
|
Thalassiosira pseudonana
(Marine)
|
Silicate starvation
|
n/a
|
n/a
|
Increased in natural lipid abundance occurred faster and to a higher extent than when starving the cells to nitrogen.
|
[8]
|
Chaetoceros gracilis
(Marine)
|
Silicate starvation
(7.6 – 30 µM Si)
|
FSW enriched with nutrients; 12:12 light:dark cycle, 100 µmol photons m-2 s-1; 25 °C. Initial Si concentrations 2-50 µM
|
1.3 ± 0.04 for all Si concentrations
|
A maximum of 46% lipids of dry weight.
Value is reported by re calculating lipid carbon contents using biochemical compulsion calculation.
|
[9]
|
Cyclotella cryptica
(Marine)
|
Silicate starvation
|
85 μmol photons m2 s-1, 1 % CO2, 23 – 25 °C
|
1.24 (normal)
0.62 (silicon deficient)
|
Increased lipid content from 20% to 28% of dry weight after 12 h of silicon deficiency
|
[10]
|
Cyclotella sp.
(Marine)
|
Silicate starvation
(3.1-49.3 µM Si)
|
FSW enriched with nutrients; 12:12 light:dark cycle, 100 µmol photons m-2 s-1; 25 °C. Initial Si concentrations 2-50 µM
|
1.4 ± 0.08 for all Si concentrations
|
A maximum of 61% lipids of dry weight.
Value is reported by re calculating lipid carbon contents using biochemical compulsion calculation.
|
[9]
|
Hantzschia sp.
(Marine)
|
Silicate starvation
(2.1-45.7 µM Si)
|
FSW enriched with nutrients; 12:12 light:dark cycle, 100 µmol photons m-2 s-1; 25 °C. Initial Si concentrations 2-50 µM
|
1.6 ± 0.08 for all Si concentrations
|
A maximum of 54% lipids of dry weight.
Value is reported by re calculating lipid carbon contents using biochemical compulsion calculation.
|
[9]
|
Navicula pseudotenelloides
|
Silicate starvation
|
Artificial seawater and an array of SERI media and conditions
|
2.5 at 30 25 °C
|
43% lipids of dry weight under Si starvation.
|
[11]
|
Navicula acceptate
|
Silicate starvation
|
Artificial seawater and an array of SERI media and conditions
|
1.5-3
|
47% lipids of dry weight sunder Si starvation.
|
[11]
|
Navicula pelliculosa
(Freshwater)
|
Silicate limitation (50 hours)
|
Tryptone (Difco) medium, 20 °C, and 17,000 lux (~230 µmol photons m-2 s-1).
For Si limitation - Si (8 µg mL-1),
|
n/a
|
Lipids were 25% of the dry weight during exponential phase.
Lipid content increased by 36% to reach 34% of dry weight.
|
[12]
|
Nitzschia dissipata
|
Silicate starvation
|
n/a
|
2.5
|
An average of 46% lipids of dry weight under Si starvation.
|
[11]
|
Phosphorus limitation/starvation
|
Phaeodactylum tricornutum
(Marine)
|
Phosphorus limitation
|
F/2 medium, 70-90 μmol photons m2 s-1, 23 – 25 °C
|
1.06 (normal)
0.53
(moderate limitation)
0.047 (limited)
|
Total lipid content increased from 8% to 16% of dry weight.
TFA constituted 41% of the total lipids.
|
[13]
|
Chaetoceros sp.
(Marine)
|
Phosphorus limitation
|
F/2 medium, 70-90 μmol photons m2 s-1, 23 – 25 °C
|
1.29 (normal)
0.006 (limited)
|
Total lipid content increased from 8% to 19% of dry weight.
Total fatty acids constituted 43-46% of the total lipids.
|
[13]
|
Combination of nutrients limitation/starvation
|
Stephanodiscus minutulus
(Freshwater)
|
Silicate, nitrogen or phosphorus limitation
|
COMBO medium, 80 μmol photons m-2 s-1 14:10h L:D, 16 °C.
|
0.17-0.84
|
Up to 50% increase in the percentage of lipids from dry weight. From 34% to 51% lipids from dry weight under Si limitation.
|
[14]
|
Temperature stress
|
Phaeodactylum tricornutum 2038 (obtained from the Institute of Oceanography, the Chinese Academy of Sciences, Qingdao)
(Marine)
|
Temperature stress
|
F/2 medium (increased 4-fold urea and 2-fold phosphate), 130 μmol photons m-2 s-1 16:8h L:D; 25, 20, 15, or
10 °C
|
n/a
|
EPA and PUFA increased by 120% after shift from 25 °C to 10 °C for 12 h.
The percentage of PUFA from total lipids increased from 22% to 32%, reaching as high as 4.9% of the total dry weight.
The percentage of EPA from total lipids increased from 13% to 24%, reaching as high as 2.6% of the total dry weight.
|
[15]
|
Chaetoceros sp.
CS256)
(Marine)
|
Temperature stress
|
F/2 medium, 80 μmol photons m-2 s-1 12:12h L:D, pH 8.3; 25,
27, 30, 33 and 35 °C.
|
0.74 (at 25 °C) - 0.87 (at 30 °C)
|
Total lipid per dry weight increased from 12 % at 35 °C to 16.8% at 25 °C
|
[16]
|
Light and UV stress
|
Phaeodactylum
Tricornutum
(Marine)
|
UV radiation
|
Natural seawater enriched f/2 medium, 60 μmol photons m-2 s-1 16:8h L:D, 18 °C.
|
1.38 (normal conditions)
|
Increase of PUFA and a reduction of SFA.
|
[17]
|
Thalassiosira pseudonana
(Marine)
|
Light and photoperiod
|
G2 medium, 20 °C, 1% CO2; 100 μmol photons m-2 s-1 12:12h L:D, 100 μmol photons m-2 s-1 24:0h L:D, 50 μmol photons m-2 s-1 24:0h L:D.
|
1.9 (100 μmol photons m2 s-1 12:12h L:D)
1.5 (100 μmol photons m2 s-1 24:0h L:D)
1.0 (50 μmol photons m2 s-1 24:0h L:D)
|
Total percentage of lipids from dry weight increased from 21% during logarithmic growth phase to 31% in stationary growth phase.
Under high light - Percentage of TAG from total lipid increase from 7-10% in logarithmic growth phase to 47% during stationary growth phase (100 μmol photons m2 s-1).
|
[18]
|
Chaetoceros muelleri
(Marine)
|
UV radiation
|
Natural seawater enriched f/2 medium, 60 μmol photons m-2 s-1 16:8h L:D, 18 °C.
|
0.8 (normal conditions)
|
Increase of PUFA and a reduction of SFA.
|
[17]
|
Chaetoceros simplex
(Marine)
|
High UV-B radiation
|
F/2 medium, 85 μmol photons m-2 s-1 12:12h L:D, 20 °C.
|
n/a
|
Increase of total lipid content by 67% under high UV-B treatment.
|
[19]
|
Cyclotella meneghiniana (Kütz)
(Marine)
|
Light intensity and phosphorus supply
|
WC medium; 30, 60, 140,
230, and 490 μmol photons m2 s-1; 20 °C
|
n/a
|
Higher levels of TFA, SFA, and MUFA with increasing light intensity.
TFA increased from 400 to 460 µg/mg C in the high-P cultures, and from 400 to 570 µg/mg C in the low-P treatment with light.
|
[20]
|
Nitzschia closterium
|
Light
|
Synthetic seawater,
17 °C, 1% CO2; ~30 and ~300 μmol photons m-2 s-1
|
n/a
|
TFA increase from 7.6% to 12.6% of dry weigth (66% increase).
TGAs increased from 1.7% to 9.2 of dry weight (440% increase).
|
[21]
|
Phaeocystis Antarctica
(marine)
|
High UV-B radiation
|
F/2 medium, 85 μmol photons m-2 s-1 12:12h L:D, 20 °C.
|
n/a
|
Increase of total lipid content by 1000% under high UV-B treatment.
|
[19]
|
Cell cycle inhibition
|
Thalassiosira pseudonana
(Marine)
|
Nocodazola
|
n/a
|
n/a
|
Increased in natural lipid abundance occurred faster and to a higher extent than when starving the cells to nitrogen.
|
[8]
|
Nitzschia sp.
(freshwater)
|
Using old sterile media of Nitzschia sp. With sufficient nitrogen source
|
80 μmol photons m-2 s-1, 30 °C, 1.5% CO2 bublling
|
n/a
|
Increase of 142% in lipid content after 1 day, and 542% of the lipid content in 4 days.
|
[22]
|
Other environmental/chemical manipulations
|
Phaeodactylum tricornutum
|
Addition of 0.88 mM sodium tungstate (without Molibdinum)
|
ASW based F/2, 300 μmol photons m2 s-1 white fluorescent, continuous light, 18 °C
|
0.97 (+N);
0.27 [2]
|
TFA increased by 67%, from 2.39 to 3.99 pg cell-1
Quantum requirement for incorporating FA, increased by 162%.
|
[3]
|
Phaeodactylum tricornutum
|
Addition of 0.88 mM sodium tungstate (without Molibdinum)
|
ASW based F/2, 200 μmol photons m2 s-1 white LED, continuous light, 18 °C
|
0.86 (+N);
0.66 [2]
|
TFA increased by 14%, from 2.9 to 3.3 pg cell-1
Quantum requirement for incorporating FA did not change.
|
[4]
|
Nitzschia laevis (UTEX 2047)
(Marine)
|
Salt stress
|
Modified Lewin’s medium, NaCl was adjusted to 5, 10, 20, and 30 g L-1.
|
From 0.58 at 10 g NaCl L-1
to 0.41 at 40 g NaCl L-1
|
Percentage of TAGs from total lipids increased from 37% to 69% when reducing NaCl from 30 g L-1 to 10 g L-1.
Percentage of natural lipids from total lipids was increased from 43% to 79% when reducing NaCl from 30 g L-1 to 10 g L-1.
|
[23]
|
Genetic manipulations
|
Cyclotella sp. wild type CYCLOJ5
(Marine)
|
Random mutagenesis using ethylmethylsulfonate
|
30 μmol photons m-2 s-1 continuous light
50% ASW
|
WT grow faster (3.45 d-1) then the CM1 mutant (3.3 d-1).
|
The light intensity at which photosynthesis saturates was 2-3 times greater in the pigment mutant CM1-1.
No improvements in biomass productivity were observed in either semi-continuous laboratory cultures or outdoor ponds.
|
[24]
|
Cyclotella cryptica T13L (Marine)
|
Expressing of Acetyl-CoA caboxylase (acc1) from C. cryptica T13L
|
50 μmol photons m-2 s-1, 16:8 dark/light
50% ASW
|
n/a
|
Transformants did not exhibit increase in oil production.
Over-expression of acc1 led to a 2-3-fold in enzyme activity
|
[11, 25]
|
Phaeodactylum tricornutum
CCMP632
(Marine)
|
Over expression of 2 different plant thioesterases:
myristic acid biased (C14-TE) and lauric acid biased thioesterase (C12-TE) from from Cinnamomum camphora
|
60 μmol photons m-2 s-1 continuous light
50% F/2- Si
22 °C
|
Slower growth observed in the transgenic strains
|
Increased accumulation of short saturated chain length fatty acids with no significant increase in secretion of fatty acids.
|
[26]
|
Thalassiosira pseudonana
(Marine)
|
Knockdown of a multifunctional lipase/phospholipase/acyltransferase Thaps3_264297
|
Continuous illumination or a 12 h:12 h light:dark cycle at 150 µmol μmol photons m-2s-1 at 18–20 °C
ASW medium supplemented with biotin and vitamin B12
|
Antisense-expressing knockdown strains exhibited wild-type–like growth
|
Transformants showed 2.4- and 3.3-fold higher lipid content than wild-type during exponential growth, and 4.1- and 3.2-fold higher lipid content than wild-type after 40 h of silicon starvation.
|
[27]
|
References for Table S1
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