Fatty acid productivity of - PowerPoint Presentation

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Fatty acid productivity of Scenedesmus obliquus under nitrogen starvation in mixotrophic cultivation exceeds the combination of autotrophic and heterotrophic cultivations

Xiao-Fei SHEN (Ph.D. Candidate)Department of ChemistryUniversity of Science and Technology of Chinasxf0912@mail.ustc.edu.cn

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Content

2. Materials and Methods

3. Results and discussion

4. Conclusions

1. Background

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Content

3. Results and discussion

4. Conclusions

1. Background

2. Materials and Methods

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University of Science and Technology of China1.Background-Comercial production obstacle

Select species

Cultivation

Oil extraction and

transesterification

Nutrient, light, water, carbon source

Lipid productivity

Biomass productivity

Lipid content

Harvest

Background

Biodiesel

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University of Science and Technology of China

Nitrogen starvation

Lipid productivity decrease

The effect of P concentration on biomass and lipid productivities of microalgae under nitrogen starvation conditions

Role of phosphorus

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Autotrophic cultivation of S. obliquus

FAME productivity:

N

starvation

conditions >

N sufficient

conditions;

N-

&P > N-&P-

lim

> N-&

P-

Bioresource

Technology

. 2014, 152: 241–246

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Both

the highest FAME productivity and FAME yield were also obtained under N-&P.

FAME

productivity under nitrogen starved conditions increased fourfold than that under nitrogen sufficient conditions.

Applied

Energy

. 2015, 158: 348–354

Heterotrophic cultivation of

S. obliquus

with acetate

55.9mg/L/d

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The cell concentration and lipid production of mixotrophic Chlorella sp. was even higher than the sum of those from photoautotrophic and heterotrophic culture.The lipid production of Chlorella vulgaris under mixotrophic cultivation was lower than under heterotrophic cultivation due to the unsatisfactory lipid content (13.8%) of mixotrophic culture

Whether

oil production from

mixotrophic

culture can

exceed

the sum of those from

autotrophic

and

heterotrophic

culture

？

Contradictory conclusions

from previous studies

Influence factors?

Algae species

and

carbon source

Nitrogen starvation

can significantly increase the lipid content and the lipid productivity of microalgae in both autotrophic and heterotrophic systems

Mixotrophic cultivation

Scenedesmus obliquus

Acetate

Nitrogen starvation

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Content

3. Results and discussion

4. Conclusions

1. Background

2. Materials and Methods

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Algae species: Axenic Scenedesmus obliquus

NIES-2280Basic medium: BG-11 medium5 g·L

-1

sodium acetate

was added as organic

carbon source

Nitrogen

source was removed from the

media

Phosphorus

concentration:

40

mg·L

-1 (

Sufficient)

Proteomics analysis

: the isobaric tags for the relative and absolute quantitation technique (iTRAQ)

Materials and Methods

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Calculation of biomass productivity

and fatty acid productivity

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Calculation of fatty acid yield

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3. Results and discussion

Content

2. Materials and Methods

4. Conclusions

1. Background

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During the whole cultivation period, the biomass productivities of the mixotrophic culture exceeded the combination of the autotrophic and heterotrophic cultures.These two absorption curves are very similar, and no significant difference was found between the assimilation rates from the heterotrophic and mixotrophic cultures

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At the end of the experiment, the fatty acid contents of the autotrophic, heterotrophic, and mixotrophic cultures were 19.7, 46.7, and 58.3%, respectively. The

highest fatty acid content was obtained in the mixotrophic culture. The fatty acid content of all the three groups rose steadily and significantly.

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C18:1 was the most predominant composition, accounting for 52.8% and 66% of the total fatty acids in the mixotrophic and heterotrophic cultures, respectively.The highest unsaturated fatty acid content was obtained in mixotrophic culture

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The protein contents of all the three systems decreased significantly during the cultivation period The lowest protein content was obtained in the mixotrophic culture; it declined sharply from 55.6% to 9.1% during the nine-day cultivation period.

No significant difference was observed between the results for the heterotrophic and mixotrophic cultures

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Fatty acid productivity (mg/L/d)

Fatty acid yieldAutotrophic14.7±2.1

-----Mixotrophic

118.4±6.4

0.45±0.04*

Heterotrophic

57.5±5.3

0.23±0.02

Note: the fatty acid produced through autotrophic process has been deducted.

More

assimilated acetate is directed to lipid synthesis rather than protein and starch accumulation with the presence of light and supply of CO

2

.

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Proteomics analysis

1,065 proteins were identified299 proteins had significant changes in the expression levelSome proteins participated in growth and lipid synthesis processes

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AccessionBiological process

Protein namePeptides (95%)Fold change

CV

Expression

A8IWA6

Growth

Glutamate synthase, NADH-dependent

15

1.71

0.10

Up-regulated

A8HNQ7

Lipid metabolism

Thioredoxin reductase

1

2.42

0.37

Up-regulated

A8IRQ1

Lipid metabolism

Ribose-5-phosphate isomerase

7

1.77

0.01

Up-regulated

A8JGJ6

Lipid metabolism

Mg protoporphyrin IX S-adenosyl methionine O-methyl transferase2

1.77

0.04

Up-regulated

A8J2S0

Small molecular metabolism

Citrate synthase

3

2.74

0.10

Up-regulated

A8J0R7

Generation of precursor metabolites and energy

Isocitrate dehydrogenase

1

2.60

0.14

Up-regulated

A0A0D2K714

Carbohydrate metabolism

Pyruvate kinase

15

2.17

0.09

Up-regulated

B6E5W6

Carbohydrate metabolism

Glucose-6-phosphate isomerase

9

1.71

0.10

Up-regulated

A0A0D2NR30

Catabolic process

Glycerol-3-phosphate dehydrogenase

2

2.52

0.23

Up-regulated

A8I8Z4

Lipid metabolism

Ribosomal protein

2

0.59

0.10

Down-regulated

A8IKQ0

Lipid metabolism

Fructose-1,6-bisphosphatase

4

0.52

0.22

Down-regulated

D8TTF7

Lipid metabolism

Plastid acyl-ACP desaturase

2

0.15

0.22

Down-regulated

A0A0D2JX51

Small molecular metabolism

Malate dehydrogenase

16

0.65

0.19

Down-regulated

Q4U1D9

Biosynthetic process

Soluble starch synthase III

3

0.58

0.10

Down-regulated

Q8VXQ9

Carbohydrate metabolism

Glyceraldehyde-3-phosphate dehydrogenase A, chloroplast

20

0.24

0.48

Down-regulated

TCA cycle

The

activity of the TCA cycle is improved in mixotrophic culture, resulting in more fatty acid synthesis in

S. obliquus

cells.

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Content

2. Materials and Methods

3. Results and discussion

4. Conclusions

1. Background

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Under nitrogen starvation, the biomass and biodiesel productivities of mixotrophic S. obliquus exceeded the combination of autotrophic and heterotrophic cells when using acetate as carbon source.

The fatty acid yield from mixotrophic culture (0.45) was almost two times greater than for heterotrophic culture (0.23).

Proteomics

analysis revealed that the activity of the

TCA cycle

was improved in mixotrophic culture when compared with heterotrophic

culture.

Conclusions

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Thank You For

Your Attention!