Wisconsin scientist studies microbes from the Dane County landfill

In Spring 2021, Erica Majumder and students from her lab arrived at the Dane County landfill in Madison, with shovels and buckets. 

They were there to collect trash. And, ultimately, study the microbes that help degrade it. 

“A landfill breaking down stuff is all about microbiology,” said Majumder, who is an assistant professor of bacteriology at the University of Wisconsin–Madison. 

While she was there, Majumder saw plastic items that were decades old. The microbes living in the landfill hadn’t degraded the plastic yet.

“It was sort of like watching your life in trash,” Majumder said. “Acne wash that I used when I was a teenager… I recognized it immediately.”

Majumder and her students brought the trash, in carefully sorted bags, back to the lab.

“We were kind of trying to answer the question of: Why aren’t microbes eating the plastics?” she said. 

One possibility: other trash is easier to digest. 

“In a landfill, there’s so many other types of trash that are easier for a microbe to eat than plastic,” she said. “So that’s probably a big reason why they’re not.”

Microbes have a hard time breaking down common oil-based plastics, because they have hard “crystalline” chemical structures, Majumder said. 

“If we did figure out maybe what was preventing them from degrading plastics, we could design a solution that would help us to solve that problem,” Majumder said. “But we have not gotten there yet.”

Engineering ‘bioplastics‘

What she has found, in a separate line of research, is how microbes can help create so-called “bioplastics” that break down easier. 

Unlike traditional oil-based plastics, bioplastics are made from renewable plant materials, like sugar. 

“To me, it doesn’t make sense to dig in the ground and do lots of extraction if there’s already these materials available to us,” Majumder said.

Her studies are using byproducts from agricultural operation, such as acid whey from Greek yogurt production. 

Using agricultural byproducts could be a more affordable way to make bioplastics, compared to sugar used in food production, Majumder said.

“Since it’s being thrown away, it’s not being used for anything else,” she said.

In a recent study, Majumder’s lab helped tap into another waste stream, from paper mills. 

“There’s just a point in the processing where you can recycle paper for so long, but then eventually you get these pieces that are too small to be recycled,” Majumder said. 

Along with a collaborating lab at the State University of New York College of Environmental Science and Forestry, Majumder’s team essentially fed broken down sugars from the paper pieces to an Escherichia coli (E. coli) microbe.

The result was a compound that could be used to build bioplastics that are also biodegradable. 

In pursuit of a ‘circular bioeconomy‘

Ultimately, Majumder hopes her work helps fuel a “circular bioeconomy,” where biological materials are re-used in production to reduce waste. 

For example, bioplastics could be broken down by microbes into building blocks for new bioplastics. 

“There’s ideally no actual waste,” Majumder said.