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Update: Yale students may have plastics breakthrough

By: Vince Bond Jr.

August 25, 2011

NEW HAVEN, CONN. (Aug. 25, 1:15 p.m. ET) — During a two-week class trip to the Amazon Rainforest in 2008, Yale student Pria Anand felt she was heading into uncharted territory.

She didn’t realize how right she was.

Anand, who collected dozens of fungal samples in Ecuador with classmates in her Rainforest Expedition and Laboratory course, wanted to find endophytes that could break down plastics in a process called bioremediation. Endophytes are microbes that can live symbiotically in plants for at least part of their lives without harming them.

After a myriad of tests at the university’s lab in New Haven, Conn., Anand found that Pestalotiopsis microspora could degrade polyurethane, a potentially groundbreaking discovery for the waste management industry.

Polyurethane is a widely-used plastic in many products, including insulation, sealants, electronics and appliances.

“Hopefully, it will be a useful tool in managing waste,” said Anand, now a medical student at Stanford University. She graduated from Yale in 2010.

The plastic, which was in a milky-white liquid form before being introduced to the fungus, had vanished when she checked on the mixture in a Petri dish two weeks later.

Anand, 23, said it was an amazing feeling. And hiking through a rainforest didn’t hurt either.

“It was really exciting. You could see that these microbes were able to break down plastic,” Anand said. “The white substance turned clear. It seemed like a long shot, so it was exciting to see that it worked.”

The fungus isn’t the only one to degrade polyurethane, but it’s special because it can do so under anaerobic conditions, or without oxygen, said Yale biochemistry Professor Scott Strobel, who oversaw the project.

Anand initially screened 60 organisms and found activity among Pestalotiopsis. She then gathered all of the related organisms and screened them further, Strobel said.

Anand’s efforts laid the groundwork for Jonathan Russell, a 2011 Yale graduate, to build on the research.

Russell, who begins work on his doctorate in molecular biology at Harvard this fall, examined the endophyte’s digestive functions and found that it could grow on polyurethane as its only carbon source.

Russell also discovered that it can grow anaerobically.

“I went after the enzymes,” said Russell, 22. “I am very excited by the chemistry that underlies biological phenomenon so I was naturally very curious about what factor was responsible for the degradation of the polyurethane.”

The Amazon basin’s plant diversity brings the class back each year in search of microbes that “have taken up residence within plants,” Strobel said.

In short, more plant diversity equals more opportunities to find helpful microbes.

The Applied and Environmental Microbiology journal will publish the findings in September.

In the future, Strobel said he hopes to characterize the protein the fungus produces that is responsible for bioremediation.

In the meantime, students are looking into ways to degrade polystyrene.

“We are also developing approaches to identify organisms able to degrade more complicated polymers. One of the students this year is targeting polystyrene,” Strobel said. “Because of the nature of the polymer, that is a much more difficult challenge than polyurethane.”