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In recent years, scientific research has been trying to solve the problem of plastic waste management. Some studies, for example, look at the degradation of non-recycled PET plastic with a natural enzyme called PETase. However, this solution still included many shortcomings preventing it from being applied on a large scale. A new study involving artificial intelligence based on machine learning has predicted the mutations needed for this enzyme to digest different kinds of plastics depending on the environment in which they are found. The new mutated enzyme, called FAST-PETase, degraded PET plastic in record time (24 hours). It is also able to repolymerize plastic and offers a sustainable and low-cost recycling solution.
Despite waste management efforts, plastic remains among the biggest pollutants in the environment. However, global plastic production continues to grow by millions of tonnes each year. And despite the various recycling solutions available today, we continue to produce new plastic because recycling is still too expensive. Between 1993 and 2015, this production has continued to climb, rising from 162 million to 448 million tons per year. Even more striking: nearly a million drinks distributed in plastic bottles are sold every minute around the world.
Only a tiny portion of plastic waste is then reused and the vast majority ends up in nature, threatening natural ecosystems in a dramatic way. Since 2015, we have indeed generated more than 6.9 billion tonnes of plastic waste, of which only 9% has been recycled. 12% was incinerated while 79% is accumulated in landfills or released into nature. Plastic is so ubiquitous that it now infiltrates everywhere and puts the lives of many living beings in danger, including humans.
These figures show how each harmful action can either completely upset the balance of our environment, or, by adopting more responsible practices, change the situation positively. It is with this in mind that the University of Texas at Austin is exploring an enzymatic process that could allow a more circular management of plastic. From a bacterium (Ideonella sakaiensis) discovered in 2016 in Japan, this enzyme (PETase) has already been the subject of many studies, but its large-scale application encountered various problems. For example, it only activates at around 70°C, which considerably limits the environments in which it could act.
The new study published in the journal Nature will perhaps finally make it possible to apply this enzymatic process on a large scale. Using artificial intelligence based on machine learning, enzymes can be custom-tweaked to be adapted to quickly digest various plastics, even below 50°C and in a wide pH range.
” When considering environmental remediation applications, one needs an enzyme that can function in the room temperature environment. This requirement is now almost met, so our technology could have a huge impact in the future. “, explains in a communicated Hal Alper, a professor in the Mc Ketta Department of Chemical Engineering at the University of Texas at Austin and one of the authors of the new study. The results of the latter are also promising, because plastic that usually takes several centuries to degrade in nature could be depolymerized in just a few hours in the best case (a few weeks at the latest).
A circular and economical process
The American researchers’ technology is based on PET plastic, a polymer produced in large quantities around the world to make up plastic bags, drink bottles and certain fibers commonly used in textiles. This type of plastic would represent in particular 12% of the world’s waste.
The machine learning model used makes it possible to predict the mutations necessary for PETase to achieve the objectives of optimal depolymerization of PET plastics. To generate the most efficient enzyme, the technology takes into account surrounding temperatures, pHs and other physico-chemical factors. The authors of the study were thus able to test and prove the effectiveness of their new enzyme FAST-PETase (Functional, Active, Stable and Tolerant PETase) on 51 different post-consumer plastics (five different polyester fibers and fabrics and bottles of water, all made from PET).
In addition, the new enzyme is also able to reconstitute the plastic it degrades (repolymerization), which allows recycling not only less expensive (energy and financially), but also more efficient and respectful of the environment. In textiles and fashion in particular, the conventional recycling of polymeric fabrics is so difficult that these sectors are the second/third biggest polluters on the planet, just behind the oil industry. The most common methods used to degrade plastic include combustion, glycolysis and pyrolysis, all of which are very energy intensive and very expensive.
FAST-PETase can be applied at industry level to reduce their ecological footprint, but also to save material thanks to its circular process. Additionally, the researchers plan to further perfect the enzyme so that it can activate in any outdoor environment. It may thus be able to clean up the most polluted sites, such as wild dumps.
Source : Nature
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Researchers have developed an enzyme capable of degrading plastic in 24 hours
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