An enzyme variant created by engineers and scientists at the University of Texas at Austin can break down plastics that typically take centuries to degrade in just a matter of hours to days on an industrial scale, at just 122°F (50°C). The enzyme has the potential to supercharge recycling on a large scale, say the developers, and allow major industries to reduce their environmental impact by recovering and reusing plastics at the molecular level.
“Beyond the obvious waste management industry, this also provides corporations from every sector the opportunity to take a lead in recycling their products…a true circular plastics economy,” said Hal Alper, professor in the McKetta Department of Chemical Engineering at UT Austin.
The project focuses on polyethylene terephthalate (PET), a polymer found in most consumer packaging and certain fibers and textiles. It makes up 12 percent of all global waste. The enzyme was able to complete a “circular process” of breaking down the plastic into smaller parts (depolymerization) and then chemically putting it back together (repolymerization). In some cases, the plastics could be fully broken down to monomers in as little as 24 hours. A research article detailing the approach more fully was published in Nature.
Researchers at UT's Cockrell School of Engineering and College of Natural Sciences used a machine learning model to generate novel mutations to a natural enzyme called PETase that allows bacteria to degrade PET plastics. The model predicts which mutations in the enzymes would accomplish the goal of quickly depolymerizing post-consumer waste plastic at low temperatures.
Through the process, which included studying 51 different post-consumer plastic containers, five different polyester fibers and fabrics and water bottles all made from PET, the researchers proved the effectiveness of the enzyme, which they are calling FAST-PETase (functional, active, stable and tolerant PETase).
“This work really demonstrates the power of bringing together different disciplines, from synthetic biology to chemical engineering to artificial intelligence,” said Andrew Ellington, professor in the Center for Systems and Synthetic Biology whose team led the development of the machine learning model.
According to the researchers, the FAST-PETase can perform the process at less than 122°F (50°C). The team plans to work on scaling up enzyme production to prepare for industrial and environmental applications. The researchers have filed a patent application for the technology and are eying several different uses. Cleaning up landfills and greening high waste-producing industries are the most obvious. But another key potential use is environmental remediation. The team is looking at a number of ways to get the enzymes out into the field to clean up polluted sites.
The work was funded by ExxonMobil’s research and engineering division as part of an ongoing research agreement with UT Austin.