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Revision as of 13:04, 15 July 2015

PlastiCure

The Problem:

Every year, more and more plastics are produced. The production of plastic was about 190 million tons, in 2000 in the world, whereas today, it is approximatively 300 million tons per year (Fig.1). The most produced types of plastic are polyethylene (PE), polyethylene terephthalate (PET) and polypropylene (PP).

Fig.1 - Evolution of the world plastic production, in million of tons, since 1950 to 2020.1


However, today, the treatment of plastic waste is not adapted to this exponential production… In 2012, 25.2 million tons of plastic waste were produced in Europe2, among which only 26 % were recycled, while 36 % were burned in order to produce energy and the remaining 38 % were dumped or buried (Fig.2). In the end, this plastic accumulates in nature and pollutes our ecosystem, especially the oceans.

Fig.2 - Treatment for post-consumer plastics waste in 2012, in the European Union.3


The problem is accentuated by the fact that plastic waste are microparticles: in our oceans, more than 90% of the plastic particles are smaller than 5 mm, which makes it almost impossible to clean them. The worst danger comes from invisible plastic: Oxidation and especially UV radiation break the plastic in small fragments which can reach 20 micrometers in diameter. Today, the particles are becoming small enough to enter in our food chain.4 Scientists have known for a while that zooplankton often accidentally ingest ocean plastic. This way, our trash works its way up our food.5


Our solution:

PlastiCure is a biological system based on E. coli designed to degrade PET (one of the main component of plastic pollution) and use the degradation products to produce bio-active compounds. The challenge of the project is coupling these two biosynthetic pathways in one system. The idea here is first to create a new way to treat plastic waste but also to produce from plastic a novel profitable transformation product that will increase efforts in plastic recycling.


The challenge of the project is to couple the PET degradation pathway with an optimised biosynthetic pathway in one system. The idea here is to create a new way to treat plastic waste and to increase efforts in plastic recycling : we aim to transform plastic waste into a profitable life-saving drug, Ery. Therefore, E. coli will be used as a heterologous host to integrate exogenous DNA sequences in multiple operons (82 % of our designed operons will be composed of heterologous genes). By this NEW WAY we will allowed E. coli to express all biodegradation / biosynthesis genes and so we will favorise the revalorisation of the plastic waste into drug.


Fig.3 - Our E. coli system which is able to synthesize biologically active products
and in the same time help to cure the world from plastic pollution by its degradation.


Erythromycin is an antibiotic used by people who are found to be allergic to penicillin to treat bacterial infections which make it a frequently prescribed drug. Its important role in the hemi synthesis of new active ingredients makes also it an attractive molecule for the future. Demand is consequently very important. But today the total synthesis of erythromycin is very complex : about 50 stages, which are increasing the synthesis duration and cost.6


Recent advances in synthetic biology allowed erythromycin production in E. coli. B. Pfeifer and H. Zhang have published in 20107 a system of 4 plasmids working in E. coli and leading to a erythromycin production with yield of 10 mg per liter of culture media.

Fig.4 - The very complex molecule of erythromycin A.8


Moreover, PlastiCure is a well-designed biological system that is composed of 2 exchangeable modules: degradation and synthesis. In fact, we can think of replacing the erythromycin production pathway by another module to transform plastic waste into a multitude of profitable molecules. Therefore, PlastiCure has been thought to be derived so we can use the plastic degradation module of our system to produce a broad diversity of products. This makes PlastiCure one of the most flexible and most innovative project.



References

1 - Plastics – the Facts 2014. An analysis of European plastics production, demand and waste data

2 - http://www.planetoscope.com/petrole/989-production-mondiale-de-plastique

3 - Plastics – the Facts 2014. An analysis of European plastics production, demand and waste data

4 - http://app.dumpark.com/seas-of-plastic-2/#oceans

5 - https://www.youtube.com/Plankton-eating-plastic

6 - http://erythromycin.org/erythromycin

7 - Haoran Zhang, Yong Wang, Jiequn Wu, Karin Skalina, and Blaine A. Pfeifer (2010).
      Complete Biosynthesis of Erythromycin A and Designed Analogs Using E. coli as a Heterologous Host.
      Chemistry & Biology 17, 1232–1240.

8 - https://en.wikipedia.org/wiki/File:Erythromycin_A.svg

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