"Nature": In the shortest day, the plastic is completely degraded! The plastic pollution problem ushers in a major breakthrough

▎ WuXi AppTec content team editor

▲ Video showing how plastics change in 48 hours with the help of the latest enzymes (Video credit: The University of Texas AT AUSTIN / Cockrell SCHOOL of ENGINEERING)

Every year, the world produces a staggering 300 million tons of plastic, but when they end their mission, what to do with these stable polymers becomes a challenge. Around the world, billions of tons of plastic waste are buried in landfills, polluting local soils and water sources, and can also appear in the form of microplastics in the blood, feces and even placenta of the human body...

How to alleviate the increasingly severe plastic crisis has become an extremely urgent challenge at present. Scientists are also looking for innovative countermeasures. Last year, a Nature paper led to an important breakthrough: a team at the University of California, Berkeley, invented a biodegradable plastic: Under composting conditions at 40°C, the plastic can be degraded in just two days.

A year later, another Nature paper proposed solutions from different perspectives. Professor Hal Alper's team at the University of Texas at Austin used machine learning to engineer an enzyme that can reduce the degradation time of plastics in centuries to hours to days. This key issue concerning the future of mankind has ushered in the hope of cracking.

Globally, less than 10% of plastic is recycled. Over the past decade, a lot of research has been made on enzymes that degrade plastics. But one unanswered question is how to make enzymes that work effectively at low temperatures, enabling low-cost, large-scale industrial applications.

What this study is trying to degrade is polyethylene terephthalate (PET), which is mostly contained in the plastic packaging we use every day. PET accounts for 12% of the world's solid waste, and if it can be rapidly degraded by enzymes and then polymerized or converted into other products, it is expected to achieve a circular carbon economy and significantly reduce environmental pollution.

In nature, an enzyme called PETase can degrade PET, but there are also obvious drawbacks: it can only work within a specific pH and temperature range, and the reaction speed is limited, and the plastic needs to be pretreated before degradation.

In this study, Professor Alper's team used machine learning models to transform PETase. Machine learning models can predict which mutations will allow PETase to rapidly degrade discarded plastic products at low temperatures, and guided by the model, the research team eventually engineered a completely new enzyme: FAST-PETase (functional, active, stable and tolerant PETase).

▲ Machine learning tools guide the research team to find a direction to improve the efficiency of enzymes (Image source: Reference[1])

This enzyme can depolymerize PET and degrade it into small molecules under a range of different pH conditions below 50°C. Under some conditions, these plastics can be completely degraded into monomers in just 24 hours.

In order to test the effectiveness of FAST-PETase in degrading different PET plastic products, the study used FAST-PETase to degrade 51 untreated PET plastic products, including various plastic containers, polyester fibers and fabrics. As a result, all plastics are completely degraded within a week, with the fastest taking only 1 to 2 days.

FAST-PETase is used to degrade many different PET plastics (Image source: Reference[1])

This enzyme can help companies recycle and reuse plastics at the molecular level, thereby reducing adverse environmental impacts. Professor Alper said: "With this state-of-the-art recycling technology, there are endless possibilities for all industries. ”

Next, the research team plans to expand the production scale of FAST-PETase, laying the foundation for further industrial applications. The team is looking at several different uses: not just to clean up plastics from landfills and make industrial production greener, but also to use this enzyme to remediate the environment and clean up contaminated areas.

Because of plastic pollution, this beautiful blue planet is dying a worrying white. Now, the birth of these emerging technologies is expected to turn the plastic pollution crisis around. We look forward to the planet returning to its original, most beautiful colors.

Resources:

[2] Plastic-eating enzyme could eliminate billions of tons of landfill waste. Retrieved Apr 27th, 2022 fromhttps://www.eurekalert.org/news-releases/950900

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