Microalgae and Cyanobacteria as raw material for production of Biofuel in comparison to terrestrial crops

Microalgae and Cyanobacteria as raw material for production of Biofuel in comparison to terrestrial crops

Hi there, welcome to my website. I’m Priyadarshinee Boojhawon. I am a third year undergraduate student

majoring in Biotechnology and Biomedical Sciences.

This unit involves the biotechnology of algae where recently I’ve been working on an experiment involving algae

which I find very interesting. I’ve been reading articles to get an idea how I can do my lab report and I came across

biofuel production from algae. I found research in the biofuel production to be very interesting and the use of

microalgae and cyanobacteria for the production of biofuel compared to terrestrial crops just caught my attention.

The world has been confronted with an energy crisis due to the depletion of finite resources of fossil fuel and they

are more likely to be scarce and costly and are considered to be unsustainable.

Methods to convert biomass to competitive liquid biofuels are increasingly attractive and are receiving increased

attention.

The direct conversion of solar energy into liquid fuel using photosynthetic microorganisms such as microalgae and

cyanobacteria is an attractive alternative to fossil fuels and they have several advantages into using these

organisms.

Are Microalgae and Cyanobacteria the raw material for the production of biofuel compared to terrestrial crops?

Two scientific papers have been studied for a comparison and an answer to the question.

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Biofuels from algae for sustainable developmentAyhan Demirbas., (2010), Use of algae as biofuel sources, Energy Conversion and

Management. Volume 51, pp 2738-2749.

Phostosynthetic production of fatty acid-based biofuels in genetically

engineered cyanobacteria Lu Xuefeng. (2010), A Perspective: Phostosynthetic production of fatty acid-based biofuels

in genetically engineered cyanobacteria, Biotechnology Advances.

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Comparisons of two scientific articles related to the production of biofuels from microalgae and

cyanobacteria have been studied.

Both papers prove the same point that these photosynthetic microorganisms are theoretically a very

promising source of biodiesel compared to terrestrial crops.

Microalgae appear to be a very good source of renewable biofuel that is capable of meeting the global

demand for transport fuels. It can be converted to biodiesel, bioethanol, bio-oil, biohydrogen and

biomethane via thermochemical and biochemical methods (Demirbas, 2011).

Industrial reactors for algal culture are open ponds, photobioreactors and closed system. Algae can be

grown almost anywhere.

Cyanobacteria are advantageous organisms for industrial applications.

They are naturally transformable and have the potential to be genetically engineered for installing

biofuel producing chemical pathways cyanobacteria have been shown to be highly tolerant to the

introduction of foreign genes (Iara & Shota, 2012). Cyanobacteria has proved to be a very good source of

biofuel production in contrast to terrestrial crops.

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The term biofuel is referred to as solid, liquid, or gaseous fuels that are predominantly produced from

biorenewable feedstock. Biodiesel is produced through the chemical reactions transesterification and

esterification by chemically reacting lipids with an alcohol producing fatty acid esters. Biofuel can be

produced from both microalgae and cyanobacteria.

Microalgae are unicellular photosynthetic microorganism with growing requirements such as lights,

sugars, carbon-dioxide, nitrogen, phosphorus and potassium. They have great capacity to convert

carbon-dioxide into lipids, protein and carbohydrates in large amounts over short period of time without

competing for arable land necessary for agricultural crops. These products can be processed into both

biofuels and useful chemicals.

Cyanobacteria are photosynthetic microbes, which can absorb solar energy and fix carbon dioxide. Direct

conversion of carbon dioxide to biofuels in photosynthetic cyanobacteria

can significantly improve the efficiency of biofuel

Production and other high value chemicals by modifying

amino acid metabolic pathways by using protein

engineering and metabolic engineering and by building

non-native biosynthetic pathways.

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Figure 1 shows carbon fixation and main steps of algal biomass technologies.

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Biofuels from algae for sustainable development

Ayhan Demirbas., (2010), Use of algae as biofuel sources, Energy Conversion and Management. Volume 51, pp 2738-2749.

According to studies in this article, microalgae appear to be the only source of renewable biodiesel that

is capable of meeting the global demand for transport fuels.

Industrial reactors for algal culture are open ponds, photobioreactors and closed system.

Microalgae contain oils or lipids and fatty acid. The algal oil is converted into biodiesel through

transesterification. The algae are harvested from tanks through processes including concentration

through different processes. Oil extracted from the algae is mixed with alcohol and an acid or a base to

produce fatty acid methylesters that make up the biodiesel.

The oil content from microalgae exceeds 80% of dry weight of algae biomass. About 50% of their weight

is oil. The yield of oil per unit area is estimated to be from 19,000 to 57,000 L per acre per year, and is

200 times greater than plant/vegetable oils and can produce 30-100 times more energy per hectare

compared to terrestrial crops. The calculated cost per barrel would be only $20 while currently a barrel

of oil in the US Market is over $100.

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Different microalgae can produce different amount of product and different biofuel types as shown in

Table 1.

Biodiesel produced from microalgae is more beneficial compared to conventional crops since it produces

more oil, consume less space and can be grown on any land even those that are not suitable for

agriculture.

However one disadvantage of microalgae for production of biofuel is the low biomass concentration. But

the high growth rate of microalgae makes it possible to satisfy the high demand on biofuels.

The advantages and disadvantages of biofuel production using microalgae are shown in table 2.

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Table 1

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Table 2



Phostosynthetic production of fatty acid-based biofuels in genetically engineered cyanobacteria

Lu Xuefeng. (2010), A Perspective: Phostosynthetic production of fatty acid-based biofuels in genetically engineered cyanobacteria, Biotechnology Advances.

This article demonstrate how cyanobacteria can be exploited for biofuel production. The

cyanobacterium Synechococcus elongatus PCC7942 has been reported to produce the isobutyraldehyde

which is used primarily as a chemical intermediate to produce plasticizers, glycols, essential amino acids,

polymers, insecticides and isobutanol, a higher alcohol, produced via a keto acid pathway.

Coupled with this, microbial production of isoprene, a high volatile hydrocarbon, has been recently

demonstrated by an engineered Synechocystis sp. PCC 6803 strain.

Moreover, another higher chain alcohol of interest as a biofuel is 1-butanol is produced by S.elongatus

and it can be used as a solvent for extraction of essential oil. 1-butanol is proposed to be used as a

substitute for diesel and gasoline because of its low hygroscopicity and energy content.

Higher energy such as C5-C8 and C4-C8 can be produced by Escherichia coli.

Furthermore, biodiesel is made by transesterification of triglycerides purified from plant oils, yielding

fatty acid methyl esters and fatty acid esters. Fatty acid can be produced from cyanobacteria. For

example, Escherichia coli can be engineered to be an efficient producer of fatty acids. The free fatty acid

can be converted into biodiesel by esterification, and to alkanes and alkenes. Hence this concept has

been applied to production and secretion of fatty acids leading to production of biodiesel using

cyanobacteria.

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Figure 2 shows the proposed biosynthetic pathways for production of fatty acid-based biofuels including

fatty acid esters, fatty alcohols and fatty alkanes directly from solar energy and carbon dioxide in

cyanobacteria.

A theoretical calculation shows that the productivity of ethanol in photosynthetic organism can reach

19,800 L/acre/year. Algeno Biofuels Inc. has developed an innovative cyanobacteria-based technology

and is reported to produce ethanol at a rate of 22,680 L/acre/year. In contrast annual yield of ethanol

from corn is 1,213 L/acre/year, from sugar cane it is 2,748 L/acre/year andfrom switchgrass it is 1,247 –

3,062 L/acre/year. Clearly, ethanol production from cyanobacteria is significantly more efficient than

from plant feedstocks.

So, according to this article compared to general

eukaryotic microalgae, cyanobacteria are more

amenable to genetic manipulation for

installing biofuel producing chemical pathways.

Also, the genetic engineering platform

for cyanobacteria is well established and

cyanobacteria have been shown to be highly tolerant

to the introduction of foreign genes.

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Figure 2

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Demirbas shows that microalgae are very rich in oil. Algae are among the fastest growing plants and 50%

of their weight is oil.

He also mentioned that microalgae have much faster growth rates than terrestrial crops and that the

unit area yield of oil is 7-31 times greater than crops.

Moreover the author also compared the chemical compositions of algae from different species and he

added that different species of algae may be suited for different types of fuel.

He also added that the yield of oil per unit area is estimated to be from 19,000 to 57,000 L per acre per

year and is 200 times greater than plant/vegetable oils and can produce 30-100 times more energy per

hectare compared to terrestrial crops. Also, the cost would be 5 times cheaper than the current price.

(See Article 1 & Article 1 contd)

Lu Xuefeng showed that using cyanobacteria to produce chemicals and biofuel is a very good method.

Genetic manipulation has permitted engineering of cyanobacteria to produce non-natural chemicals

typically not produced by photosynthetic microorganisms. Cyanobacteria can be engineered to install

biofuel chemical pathways.

He also added that productivity of ethanol in cyanobacteria can be 19,800-22,680 L/acre/year while in

plants/terrestrial crops it is very low. (See Article 2 & Article 2 contd)

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Figure 3 shows the routes to biofuels, where biodiesel in microalgae is labelled as green line and novel

biofuels in cyanobacteria is labelled by red line and traditional biofuels by blue arrows.

To summarise, both papers show that microalgae and cyanobacteria produces more biofuel per year

compared to terrestrial crops since they have a rapid growth rate, CO2 fixation ability and production of

fatty acids.


Figure 3

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Ayhan Dermibas did a study on the use of algae for biofuel production and showed how it is very

beneficial compared to terrestrial crops. The claim was sufficiently supported by evidences. The use of

different industrial reactors yield to different amount of oil. Also, the cost is 5 times cheaper to the

current cost.

The study carried out by Lu Xuefeng provided evidences about the oil yield in terrestrial crops as well as

few species of cyanobacteria. More importantly he also proved how cyanobacteria proved to be the

most suitable as raw materials for biofuel production compared to terrestrial crops. The claims were

supported by evidences.

Both research articles provided evidences and they were relevant enough to prove the point of

microalgae and cyanobacteria being the most important raw material for biofuel production compared

to terrestrial crops.

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The research made on the two articles and the evidences provided were fair enough to

conclude that microalgae and cyanobacteria are better raw material for biofuel production

compared to terrestrial crops. The benefits of biofuel over traditional biofuel that is from

terrestrial crops and plants include greater energy security, reduced environmental impact,

foreign exchange and greenhouse effect issues.

In contrast the competition with land use for crops results in increased food cost, biofuel

production from terrestrial crops can cause great environmental cost, for example

deforestation to clear land crops caused emission of large amount of greenhouse gases.

The two articles were an answer to the question whether or not microalgae and cyanobacteria

are a raw material for production of biofuel compared to terrestrial crops.


• Ayhan Demirbas. (2010), Use of algae as biofuel sources., Energy Conversion and Management.

Volume 51, pp 2738-2749

• Iara M.P. Machado, Shota Atsumi. (2012), Cyanobacterial biofuel production., Journal of

Biotechnology, volume 162, pp 50-56.

• Lu Xuefeng. (2010), A Perspective: Phostosynthetic production of fatty acid-based biofuels in

genetically engineered cyanobacteria, Biotechnology Advances.

• M. Fatih Demirbas., (2011), Biofuels from algae for sustainable development, Applied Energy. Volume

88, pp 3473-3480.

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Microalgae and Cyanobacteria as raw material for production of Biofuel in comparison to terrestrial crops