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Chemist Susie Y. Dai and her team were trying to create a strain of algae that would produce aviation fuel when they stumbled upon something surprising.
Through a coincidence of science, the engineered algae turned out to be uniquely good at vacuuming up microplastics.
Dai and her colleagues at Texas A&M University realized that because of a chemical on the surface of the algal cells, the genetically modified algae they were working with might be able to help pick up tiny shards of plastic pollution in water.
They ran some tests and realized it would work.
“At that time, it was very surprising,” said Dai, now a professor at the University of Missouri. “We saw a significant removal capacity of the microplastics from the solution by our engineered algae.”
The term microplastics, first coined in 2004, has become a catch-all for the vast array of minuscule plastic particles polluting nearly every corner of the world, from the summit of Mount Everest to human brains. As scientists find microplastics in more places, they’re also searching for ways to clean them up.
Both Dai’s engineered algae and the tiny pieces of plastic are hydrophobic, meaning they repel water and attract each other. By changing the genetic code of the algae, the scientists can dial up its stickiness factor, removing more than 90% of microplastics in a water sample within an hour.
Dai and her coauthors laid out this process in a new paper in Nature Communications. The engineered algae grab hold of the microplastics, then sink to the bottom of the water. The plasticky algae sediment can then be collected and even potentially turned into a recycled product of its own.
Creating recycled materials from microplastic pollution is one of the most exciting outcomes of the research, Dai said.
"What we hope to do is upcycle the whole stuff into another bioplastic," she said. "...Not only can we remove [microplastics] from the solution, we can also make a useful product."
Microplastics are widespread in the environment, said Julie Peller, a professor of chemistry at Valparaiso University. The sun and waves break plastic down into smaller and smaller pieces over time.
“I think the more we learn, the more overwhelming you see that this problem really is,” Peller said.
She said that’s worrying because many studies have found microplastics are now inside human bodies and hurting people’s health. Microplastics are linked to a range of serious health issues, including cancers, respiratory issues and digestive diseases.
Peller’s work has focused on the Great Lakes and water systems in northern Indiana. She was not involved in Dai’s study but has done other research on how microplastics and algae interact.
Even without bioengineering, Peller has found that microplastics like clothing fibers stick to algae.
“The reality is, when this algae is in the water, it's like a little vacuum cleaner,” Peller said. “It pulls up all kinds of stuff that's in the water.”
In Peller’s view, the best way to address the microplastics problem is to cut down the use and production of plastic so less of it ends up in the environment. That can be difficult, she added, because plastic is often the cheapest option for businesses.
But, Peller said consumers have more power than they realize.
“Make it a journey,” Peller said. “Go, ‘Okay, where's the first place that I can eliminate plastic? Where's the next one, where's the next one, where's the next one?’ And over time, if people in society decide we don't want all this stuff, changes can happen.”
Peller also wants to make sure solutions to the plastics issue don’t inadvertently create more environmental issues. That’s something Dai has thought about as well — she doesn’t want a fix that ends up creating a bigger mess.
To avoid that, Dai imagines her team’s bioengineered algae would be part of a closed system, potentially an additional step in a wastewater treatment process, rather than just unleashed into bodies of water.
This is important because Dai said wastewater treatment plants are currently capable of removing bigger microplastics, but not the smallest ones.
“It’s wonderful to remove and retain the big ones, but eventually the smaller ones will be the ones really getting to the ecosystem and then getting to human exposure routes,” Dai said.
So far, Dai’s bioengineered algae seem to be good at grabbing both larger and smaller sizes of microplastics. But there are still a lot of limitations that will make it hard to scale the process up, including finding ways to grow large amounts of the algae. And she needs to study the process outside of the lab, in real-world scenarios.
Even though Dai thinks about big environmental problems all day, she said her work has kept her hopeful about the ways science can improve the world.
“We constantly as human beings live in this dilemma between new technology development and then the legacy problems that our ancestors created,” Dai said. “I don't think we need to worry about that. That's why we're here. We try to develop new methods to maintain sustainability and also make people healthier and happier.”
This story was produced in partnership with Harvest Public Media, a collaboration of public media newsrooms in the Midwest and Great Plains. It reports on food systems, agriculture and rural issues.
