Feb 25, 2021

How biofacturing can help tackle plastic waste

Zymergen scientist Elise Span shares how we can leverage the natural plastic-eating ability of microorganisms for a cleaner, more prosperous world.

Image showing plastic pieces on a metal spoon
Spoon-feeding plastics to microbes may one day solve our plastic waste problem — and create great new products.

Plastic waste is choking our landfills and polluting our water and soil. Recycling is important, but only about 9% of the world’s plastic gets recycled. The rest adds to the 6.3 billion tons of plastic waste that has accumulated across the globe.

What if we could design microbes to break down plastic and turn it into useful products? Zymergen scientist Elise Span is working on a project to do just that.

“Polyethylene is the most common and highest-volume plastic in the world,” she says, “accounting for over 100 million tons produced annually.” Polyethylene is commonly used to make shopping bags, garbage bins, and containers for everything from milk to bleach. Elise’s project is focused on creating microbes that break down polyethylene into compounds that can be transformed into useful products.

Zymergen scientist, Elise Span

“We can break down polyethylene into building blocks for recycling,” she says, “or theoretically make upcycled products for electronics, materials, fashion, or other consumer goods.”The project was inspired by talking with partners about the power of Zymergen’s metagenomic database. This database is an enormous collection of natural molecular diversity that we can use to design products with never-before-imagined properties. “They had seen news articles about using enzymes to break down PET plastic bottles. They wondered if similar enzymes could be found in our database to break down polyethylene, or PE, which is much more difficult to degrade.”

Elise and her team seek to use Nature’s abilities to break down what she calls the “devastatingly durable” materials that we have introduced into our environment.

“We are trying to partner with and better understand the natural world to uncover these secrets and find a realistic, sustainable solution to plastics waste.”

Elise is optimistic about finding and optimizing a natural solution. That’s because certain microbes already have evolved processes to break down and utilize plastic as a food source. But in nature, these processes are very, very slow.

“My belief and hope is that we can apply our technology to rapidly break down plastics into useful substances,” she says.

Plastic is uniquely tough to break down, especially polyethylene. It is also not a substance that biologists typically incorporate into experiments. At the start of the project, Elise was worried about how the team would even make the culture medium in which the microbes would grow. Polyethylene, like a solid oil, doesn’t mix with water and won’t readily disperse in aqueous growth media. “And if you can’t make the media,” says Elise, “you can’t grow or study many microbes.”

Plastic growth medium for Zymergen’s early microbial discovery work

“One great thing about Zymergen is we have folks with all kinds of backgrounds, including materials science.” A cross-pollination of ideas from across the company got it to work, and that was our first celebratory moment. “I remember standing in the hallway with a Petri dish of milky white agar in my hand and a big grin on my face,” Elise says.

Making the project even more challenging, Elise explains, is that the basic science around PE biodegradation is so limited. There are reports that provide some clues, but a lot of discovery work needs to be performed for this to work at an industrial scale. “With this project,” she says, “we started pretty far back, asking questions like: What enzymes and microbes might work? And then, what kinds of products can and should we make?”

Despite the challenges, Elise and her team have already discovered microbes that naturally degrade PE, sped up the process, and gathered useful insights into the pathway. “But there’s definitely more to investigate as we guide microbes toward degrading plastic.”

Image showing plastic bag floating in the ocean

As inspiring as the early scientific results have been, Elise says the most exciting aspect is that Zymergen is taking on a big problem like this in the first place.

“We believe in the power of our technology platform to tackle something really hard like this,” she says. “Our platform will help us design the best microbe for the task, building on our discoveries to move faster as new knowledge is plugged back into the platform.” She’s also inspired by her teammates, “from the courage and scrappiness of the people on the core team, to others’ willingness to consult or pitch in where they can be of help. We are working hard and aren’t afraid of failing.”

Even though turning plastic into valuable products is a very difficult challenge, it seems there’s no other project Elise would rather be working on.

“This project taps into something that I think we all want—cleaning up a polluted planet,” she says. “No one likes seeing plastic debris, whether it’s along their daily commute, or in pictures of the Pacific garbage patch. We all want to live in a cleaner environment.”

And if we can do that while also making great products, all the better.

Read more about the Zymergen initiative to tackle plastic waste.