Plastic pollution is everywhere. It's showing up as microplastics that contaminate nearly everything and even in the stomachs of dead whales. This is because a lot of plastic is simply not biodegradable and has a very long lifespan.
Researchers around the world have been coming up with ingenious solutions such as reusing plastic into building blocks and even turning it into useful oils. But still, the problem persists on a large scale.
An enzyme variant that gobbles up hard-to-degrade plastics
Now, engineers and scientists at The University of Texas at Austin have come up with an innovative solution that may just resolve our plastic woes once and for all, according to a statement released by the institution on Wednesday. The solution takes the shape of an enzyme variant that gobbles up environment-throttling plastics that typically take centuries to degrade in just a matter of hours to days.
“The possibilities are endless across industries to leverage this leading-edge recycling process,” said Hal Alper, professor in the McKetta Department of Chemical Engineering at UT Austin.
“Beyond the obvious waste management industry, this also provides corporations from every sector the opportunity to take a lead in recycling their products. Through these more sustainable enzyme approaches, we can begin to envision a true circular plastics economy.”
Results in as little as 24 hours
The new process sees plastics fully broken down to monomers in as little as 24 hours. The project focuses on polyethylene terephthalate (PET), a polymer that makes up 12% of all global waste. The enzyme is so efficient that it can even work at ambient temperature, making it suitable for a variety of uses.
The researchers are now working on scaling up enzyme production to prepare for industrial and environmental applications. These will take the shape of landfill cleanup initiatives, the greening of high waste-producing industries, and even environmental remediation. The team's study was published in the journal Nature.
Plastic waste poses an ecological challenge and enzymatic degradation offers one, potentially green and scalable, route for polyesters waste recycling. Poly(ethylene terephthalate) (PET) accounts for 12% of global solid waste5, and a circular carbon economy for PET is theoretically attainable through rapid enzymatic depolymerization followed by repolymerization or conversion/valorization into other products. Application of PET hydrolases, however, has been hampered by their lack of robustness to pH and temperature ranges, slow reaction rates and inability to directly use untreated postconsumer plastics1. Here, we use a structure-based, machine learning algorithm to engineer a robust and active PET hydrolase. Our mutant and scaffold combination (FAST-PETase: functional, active, stable and tolerant PETase) contains five mutations compared to wild-type PETase (N233K/R224Q/S121E from prediction and D186H/R280A from scaffold) and shows superior PET-hydrolytic activity relative to both wild-type and engineered alternatives12 between 30 and 50 °C and a range of pH levels. We demonstrate that untreated, postconsumer-PET from 51 different thermoformed products can all be almost completely degraded by FAST-PETase in 1 week. FAST-PETase can also depolymerize untreated, amorphous portions of a commercial water bottle and an entire thermally pretreated water bottle at 50 ºC. Finally, we demonstrate a closed-loop PET recycling process by using FAST-PETase and resynthesizing PET from the recovered monomers. Collectively, our results demonstrate a viable route for enzymatic plastic recycling at the industrial scale.