A new variant of plastic-eating enzymes can be used to clean up plastic waste and landfills.

A new enzyme variant that can break down environmentally constraining plastics, which often take centuries to degrade, in just a few hours to days. It was created by chemical engineers and scientists at the University of Texas at Austin.

The discovery, published in Nature on April 27, 2022, could help solve one of the world’s biggest environmental problems: What to do with the billions of tons of plastic waste that piles up in landfills and pollutes our natural soils and waters? The enzyme has the potential to power recycling on a large scale, enabling large industries to reduce their environmental impact by recovering and reusing plastics at the molecular level.

“The possibilities are endless across industries to take advantage of this pioneering recycling process,” said Hal Alper, a professor in the McKetta Department of Chemical Engineering at UT Austin. “Beyond the open waste management industry, this also offers companies from every industry the opportunity to lead the way in recycling their products. Thanks to these more sustainable enzyme approaches, we can begin to envision a true circular plastics economy.

The project focuses on polyethylene terephthalate (PET), an important polymer found in most consumer packaging, including snack containers, soda bottles, fruit and salad packaging, and certain fibers and textiles. It accounts for 12% of all global waste.

The enzyme was able to complete a “cyclical process” of breaking the plastic into smaller pieces (depolymerization) and then chemically reassembling it (repolymerization). In some cases, these plastics can completely break down into monomers in as little as 24 hours.

PET (polyethylene terephthalate) is the most common thermoplastic polymer resin of the polyester family and is used in fibers for clothing, containers for liquids and foods, and thermoforming for manufacturing.

Researchers at the Cockrell School of Engineering and the College of Natural Sciences used a machine learning model to create new mutations in a natural enzyme called PETase that allows bacteria to break down PET plastics. The model predicts which mutations in these enzymes will achieve the goal of rapidly depolymerizing post-consumer waste plastic at low temperatures.

In this process, which involved examining 51 different post-consumer plastic containers, five different polyester fibers and fabrics, and water bottles, all made of PET, the researchers demonstrated the efficacy of the enzyme they call FAST-PETase (functional, active). , stable and tolerant PETase).

“This work demonstrates the power of bringing together different disciplines, from synthetic biology to chemical engineering to artificial intelligence,” said Andrew Ellington, a professor in the Center for Systems and Synthetic Biology whose team led the development of the machine learning model.

The most obvious way to reduce plastic waste is recycling. But globally, less than 10% of all plastic is recycled. Besides throwing plastic into landfills, the most common disposal method is incineration; this releases costly, energy-intensive, and harmful gases into the air. Other alternative industrial processes include very energy-intensive glycolysis, pyrolysis, and/or methanolysis.

Biological solutions take much less energy. Research on enzymes for plastic recycling has advanced over the past 15 years. However, until now no one had figured out how to make enzymes that can operate efficiently at low temperatures making them both portable and affordable on a large industrial scale. FAST-PETase can operate at 50 degrees Celsius.

Next, the team plans to scale up enzyme production to prepare for industrial and environmental applications. The researchers have applied for a patent for the technology and are interested in several different uses. Cleaning up landfills and greening high-waste-generating industries are the most obvious. But another important potential use is in environmental remediation. The team is exploring various ways to field enzymes to clean up contaminated sites.

“Considering environmental cleaning applications, you need an enzyme that can work at ambient temperature. “This requirement is where our technology has a huge advantage in the future.”

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