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Revision as of 14:05, 29 July 2015

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Project description

Overview of 2015 UChile-OpenBio Team Project

Nowadays, fossil plastic contamination is still an issue. Each year, 130 million tons of plastics are produced in the world, which last between 500 to 1000 years in degrading, polluting our entire environment. A sustainable initiative is to produce biodegradable plastics, however the current synthesis process (chemical and biological) is complex and expensive. For this reason, the team UChile-OpenBio plans to engineer a biologic system, enabling it to degrade glucose in order to produce and export into the medium a biodegradable plastic called PLA. In the future the team hopes to replace the glucose for a renewable resource, the dun algae, which is located on the Chilean coasts. The aim is, in the long term, to implement a simple and cheaper system to produce bioplastic. This way, the team would help fighting the contamination due to fossil plastics.

Background

Each year, 130 million tons of plastics[1] are produced, which last between 500 to 1000 years in degrading[2] and are responsible for the death of 1,5 millions of marine animals all around the world.[3] This corresponds to a Chilean waste of up to 25 thousand tons thrown into the ocean, where it can be brought back to the coast, sunk or accumulated near the Pascua Island.[4] In Chile, the government emitted a ley project to forbid any sell of supermarket bags made of polyethylene, polypropylene and other artificial polymers non-biodegradable, which was accepted in the Patagonian territory last year. [5]


Representation of plastic contamination in the sea (ecologiaverde.com).

Fossil plastic contamination is not a new issue and several ways to reduce it have been explored. However, actions like recycling are not viable solutions, knowing that only up to the 30% of the produced plastics is actually reused. [6] A more sustainable initiative is to produce biodegradable plastics, made of renewable resources such as corn: their degradation time can be of only two years in the case of the PolyLactic Acid (PLA) and their physical properties are very similar to the classic plastic ones. [7] Nevertheless, the current synthesis, essentially driven by chemical reactions, is quite expensive because the process requires complex experimental conditions, for instance the absence of any trace of water, which raises the production costs.[2] This challenge, consisting in making the biodegradable plastic production cheaper, gave birth to another way to synthesise them: using microorganisms. Indeed, as it has been observed for the insulin, microorganisms have a great production capacity.[8] Several scientific studies already began to produce a bioplastic, PHB, with genetically modified bacterias.[9] The main difficulty resides in finding a way to export the bioplastic outside the cell. Indeed, the recuperation of cell products is a difficult and expensive challenge. Considering all these elements, the team UChile-OpenBio wants to reach, in the long term, the implementation of a secretory biological production of PLA from a renewable resource, the dun algae, which is located on the Chilean coasts. To do that, the first step consists in designing and testing the biologic system using a simple sugar: the glucose. This way, the team would help fighting the contamination due to fossil plastics.

Main Goal

For the iGEM competition, the team aims to engineer a biologic system, enabling it to degrade glucose in order to produce and export into the medium a biodegradable plastic called PLA.

The project

The team will start with the proof of concept, consisting in programming two populations of Escherichia coli to produce PLA from glucose. In a few words, the first population (in light green) will convert the glucose into an intermediate called lactate, which will be processed by the second population (in blue) to polymerize it into PLA.


A scheme representing the general process of our system.

The team is also implementing a pH-sensing system which will allow the bacteria to control the lactate production: the higher the intermediate concentration, the lower the pH, which induces a negative control in the first population of E.coli, stopping the production of lactate and by the way, of PLA. The second population of bacterias will possess an exportation system that would enable it to send the biologic PLA outside the cells, into the medium. This way, the purification of the bioplastic is easier. To ensure the safety of the persons working in the laboratory and of the environment, the team designed a safety system which consists in making arabinose-dependent the cell survival: while the bacterias grow up in laboratory conditions, defined by the presence of arabinose into the medium, the safety system is shut down. If the bacterias escape from their medium, the safety system won’t be turned off anymore and the cells will produce a toxin which will kill them.

Potential Impact

Advantages

  • Fossil plastics could be replaced in the long term by biodegradable plastics such as PLA, ending up with the environmental contamination associated.
  • The cares provided by the medical area could be improved by the expansion of biocompatible prosthesis made of PLA.
  • Digital fabrication laboratories could have better access to their feedstock (the PLA) which could promote the fabrication of Open Tools and the society empowering.

Desadvantages

    The team does not currently know what will be the nature of the produced PLA nor how will react the bacterias to the genetic modifications that have been made, so at least two consequences should be considered:
  • The biologic production of the PLA can lead to a non-utilizable bioplastic (physical state, purity, properties,…)
  • Every engineered biologic system presents human and environmental risks and must be controlled by safety rules. However it is difficult to have a complete control over the biologic system, even with the safety system implemented (any aleatory mutation can inhibit it).

Future Prospects

As said before, the project presented for the iGEM competition is only a proof concept: the team aims to bring the project beyond the academic field by changing the feedstock to a more sustainable one, the dun algae. What the team will do with the final project is still being discussed.

Sponsors

The team can already rely on the support of various institutions:
  • Centre for Biotechnology and Bioengineering
  • Department of Chemical Engineering and Biotechnology
  • National Committee of Scientific and Technologic Research
  • Sigma-Aldrich Company

References

  1. El Banco Mundial, 2014. Una bolsa de plástico para asfixiar el mar. [online] <http://www.bancomundial.org/es/news/feature/2014/12/08/bolsa-de-plastico-asfixiar-planeta> [consulted: 14-07-2015]
  2. Garlotta, 2002. A Literature Review of PolyLactic Acid. Journal of Polymers and the Environment, Vol. 9, No. 2.
  3. El Tiempo, 2014. Plásticos matan al año 1,5 millones de animales marinos. [online] <http://www.eltiempo.com/estilo-de-vida/ciencia/muerte-de-animales-por-plasticos-lanzados-al-mar/14710998> [consulted: 14-07-2015]
  4. La Tercera, 2015. Cristina Espinoza. Hasta 25 mil toneladas de plástico anuales se arrojan al mar desde Chile. [online] <http://www.latercera.com/noticia/tendencias/2015/05/659-627978-9-hasta-25-mil-toneladas-de-plasticos-anuales-se-arrojan-al-mar-desde-chile.shtml> [consulted: 14-07-2015]
  5. Chilean Senate, 2014. [online] <http://www.senado.cl/prohibicion-de-bolsas-plasticas-en-la-patagonia-votaran-idea-de-legislar/prontus_senado/2014-10-23/122842.html> [consulted: 14-07-2015]
  6. PlasticsEurope. Plásticos - Situación en 2011. Análisis de la producción, la demanda y la recuperación de plásticos en Europa en 2010. [online] <http://www.plasticseurope.org/documents/document/20111107102611-pe_factsfigures_es_2011_lr_final041111.pdf> [consulted: 15-07-2015]
  7. Serna et al. Ácido Poliláctico (PLA): Propiedades y Aplicaciones. Ingeniería y Competitividad (2003), Vol.5, 16-26.
  8. Jong et al. Production of recombinant proteins by high cell density culture of Escherichia coli. Chemical Engineering Science (2006). Vol. 61, Issue 3, 876–885.
  9. Mahishi et al. Poly(3-hydroxybutyrate) (PHB) synthesis by recombinant Escherichia coli harbouring Streptomyces aureofaciens PHB biosynthesis genes: Effect of various carbon and nitrogen sources. Microbiol. Res. (2003) 158, 19–27