Introduction
In the past 100 years, the rapid development of the traditional chemical industry has greatly promoted
the improvement of people’s material living standard. Our basic necessities of life are almost inseparable
from the chemical synthesis goods. However, the environmental pollution and energy crises have also
forced people to find new solutions. Synthetic biology instructs us that we can introduce new chemical
reactions into biological cells, thus producing high quality chemical products in a greener way.
Then what does synthetic biology "synthesize"?
Biosynthesis of synthetic biology lies mainly in the biosynthesis of natural product and synthesis of
bulk chemical. The former is represented by artemisinin, lycopene and carotene, etc., and the use
of synthetic biology method to synthesize our daily necessities of traditional chemical products
or raw materials can serve more people. Today, scientists have been able to use micro-organisms or
modified industrial enzymes to synthesize bio-plastics, bio-fuels, chemical raw materials and other
chemical products. For example, DuPont has achieved the reality of micro-algae efficiently synthesizing
isobutanol; Blupha, a well-known company to China’s iGEM teams, also has also mastered the biosynthetic
method to get PHA production. However, most of the existing products are facing the dilemma as for
the cost, making them outshined by the traditional chemical products, which in fact limits the industrial
promotion of synthetic biology.
Background
This year, we focus mainly on an important synthetic organic chemical raw material——acrylic acid. We
hope to build efficient cell factories to achieve "all green" production of acrylic acid.
What is acrylic acid?
Acrylic acid is an important synthetic organic chemical raw material. Acrylic acid and its ester compounds
are widely used in adhesives, coatings, synthetic rubber, high absorbent resin and other chemical
products.
The existing methods of producing acrylic acid
According to our current research carried out about the acrylic acid synthesis method, we list them as
follows:
1、Traditional chemical synthesis
图 Acrylic acid two-step oxidation
Propylene firstly reacts with oxygen to produce acrolein, whose deoxidation leads to the production
of acrylic acid. The conversion rate is often up to 90%, so this method is applied in most industrial
production of acrylic acid
Although this practice has many advantages, but the raw material depends heavily on the traditional
fossil energy, bringing about heavy pollution, high energy consumption and a lack of sustainability.
Therefore, it is imperative to develop renewable energy alternative to replace fossil energy to produce
acrylic acid in a greener way.
2、Acrylic acid semi-biosynthesis
Acrylic acid semi-biosynthesis refers to the method of using micro-organisms to turn acrylonitrile,
acrylamide and other petrochemical raw materials into acrylic acid.
图Acrylonitrile conversion
图Acrylamide conversion
Acrylic acid semi-biological method, although possesses the high yield, its raw materials acrylonitrile
and acrylamide cost even more than acrylic acid, which limits the industrialization of this method.
3.Acrylic acid complete biosynthesis
Acrylic acid complete biosynthesis method refers to the direct use of saccharides and other biomass
fermentation to produce acrylic acid.
图Lactate dehydration pathway
图3-hydroxypropionic acid pathway
图Propionic acid oxidation pathway
图DMSP pathway
Some shortcomings of the existing acrylic acid biosynthesis method include complexity of the synthetic
pathway , obscuration of the synthesis mechanism and low efficiency of the synthesis. How to build
a short and efficient acrylic acid biosynthetic pathway to achieve a highly efficient acrylic biosynthetic
factory is the very key to success! And this is also the entry point of our project this year.
why we choose Glycerol as cabon source
Glycerol is a simple polyol compound, which presents as viscous liquid at the room temperature. It is
colorless, tasteless and non-toxic. Glycerol is a by-product of the biodiesel manufacturing industry,
which once was a relatively scarce chemical raw material. With the rapid development of bio-diesel
manufacturing industry in recent years, the substantial increase of glycerol production has led to
the significantly lower price. Therefore, the use of glycerol as a raw material for microbial cell
factory to produce bulk chemicals has the advantage of being cheap and green, while it also allays
the pressure of dealing with the by-products waste in the production of biodiesel. In addition, compared
with glucose, xylose and other carbohydrate substrates, glycerol metabolism can produce higher reducing
power, making it the ideal carbon source for the fermentation synthesis in cell factory.
