Three years ago, Japanese scientists discovered a tiny new bacteria with an unusual ability: The organism, which lived in soil near a plastic bottle recycling plant, could eat plastic. A year later, a plastic-eating fungus was discovered in a landfill in Pakistan. The year after that, a college student discovered plastic-eating bacteria in a polluted site in Houston. Now, researchers from Hitachi and Cambridge Consultants, an engineering and product development company, plan to use synthetic biology to manufacture a similar plastic-eating enzyme. It could later be used in recycling plants or in the environment—and potentially even in the ocean, where as much as 12.7 million metric tons of plastic ends up every year.
“Attacking the problem biologically means that you have the ability to come up with a range of solutions,” says James Hallinan, business development manager of synthetic biology at Cambridge Consultants. The company, which has worked in various fields for nearly 60 years, started working in synthetic biology in 2015. “It’s really about the engineering of biology, making it predictable and definable and reproducible,” he says. “And this idea that, in the future, more and more products are going to be made via a biological process, as compared to the old traditional way of making things from chemicals, and in particular petrochemicals.”
The team has explored ways to make plastic biologically instead of from petrochemicals. But it also realized that it could use biology to begin breaking down some of the billions of tons of plastic that have landed in landfills and the environment, where it can take hundreds of years—or perhaps longer—to fully break down. A 2017 study estimated that of the 8.3 billion tons of plastic that humans had produced since the material was invented, around 6.3 billion tons ended up as waste; only 9% was recycled.
Around the world, several research projects are exploring the potential of enzymes, the part of the microorganisms responsible for digesting the plastic, to help. In the U.K., scientists studying the Japanese bacteria accidentally created a version of the bacteria’s enzyme that worked even better, breaking down plastic bottles in days rather than weeks. At the National Renewable Energy Laboratory in the U.S., scientists are also working on the enzyme—called PETase, because it can eat PET plastic—to make it work faster. Researchers in Germany studied the structure of PETase to optimize it. And in France, a startup called Carbios has developed its own enzyme, which can fully break down PET plastic so it can be recycled into new, consumer-grade plastic of the same quality as virgin PET. Major corporations including PepsiCo and Nestlé are now partnering with the company, which plans to begin building its first demonstration plant this fall.
Like some other new recycling technology, using enzymes has advantages over traditional methods of shredding up old products. The plastic doesn’t have to be clean, and can be broken down completely. “We take these plastics back down to some of their precursor components, and then they are maybe in a better position then to be reused and reincorporated into new materials,” Hallinan says. Creating precursors for making plastic, rather than recycling whole plastic into a lower-grade material, might incentivize more recycling because there’s a better market for the final product. “There might be more economic appetite, more industrial appetite, for those types of materials.”
Even more interesting is the possibility that optimized plastic-eating enzymes could be used in the environment at large, not just in recycling facilities. While the solution to the overall problem of plastic waste starts with design, and probably eliminating single-use plastic items completely, we also need to find ways to deal with all of the plastic that’s already been thrown out. The majority of plastic never makes it into the recycling stream—and we’re now seeing the consequences, from microplastics in Arctic snow to plastic in children’s bodies. Working in the environment is a more complicated proposition, as the team would have to prove that it can happen without any negative consequences and get regulatory approval.
“That’s the type of solution which is going to take a much longer time, because it’s not just about technically does this work?” Hallinan says. “Does this work in a way which makes economic sense, which fits with regulatory concerns? And you don’t want to start degrading plastics which are important to people—you don’t want your bottles of shampoo in Walmart to start degrading because this bacteria is now everywhere.”
The team is currently studying the full range of possible solutions, and then will choose a strategy; some approaches might be technically feasible but not economically viable. They’ll also decide on the best business approach. Hitachi—better known for making things like power tools and construction equipment—might develop the technology or could potentially become an end user of it. “They have a recognition that they’ve got a responsibility to both their customers and also to the planet in general to ensure that what they’re developing and the products they make for the planet are good for the planet, in the long run,” says Hallinan.