Plastic has been discovered at the bottom of the ocean, at the top of the Himalayas, embedded in Arctic sea ice and swirling in the air around us.
It is an environmental crisis that has spurred the creation of a number of plastic substitutes, many made from plants and advertised as compostable or biodegradable, though studies have shown some versions may not be either.
Now a team of scientists says it has created a possible alternative using a bacteria better known for turning stomachs. The material, which they call “aquaplastic,” is derived from Escherichia coli, or E. coli.
The bacteria lives in the gut but when ingested through contaminated food or water can land someone in the emergency room.
Using genetically engineered E. coli, scientists from Northeastern University, Harvard, Johns Hopkins and elsewhere say they turned E. coli into a plastic that can be made into plastic film or bendable three-dimensional molds for cones, bowls, tubes or other structures. The plastic substitute almost completely dissolves in 45 days, according to a study published last month in Nature Chemical Biology.
They fed the E. coli a nutrient-rich material that enabled it to produce two types of “aquagels,” flexible material they used to make different forms of aquaplastics.
“The original idea came from wanting to build materials the way biology does,” said Neel Joshi, one of the study’s authors and a professor of chemistry and chemical engineering at Northeastern.
It is like when a seed grows into a tree, he said. It absorbs “nutrients and water from its surroundings, and its genetic instructions allow it to produce a tree in the end.”
“Even after the tree is built,” he said, “the cells that built it remain active inside the tree and can provide some responsiveness to the environment and maintain the material over time, and we wanted to see if we could do a similar thing with engineered cells.”
A house made from 3D aquaplastic derived from Escherichia coli. (Laura Castanon)
The science behind these aquagels is part of a new field called “engineered living materials,” in which living materials are used to produce new substances. These materials develop some of the properties of the life it imitates and can then be used to create drugs, fuels and other products.
Joshi said E. coli is “one of the most engineerable organisms” and already has the tools needed to produce a new plastic.
“Biological systems already know how to convert greenhouse gases, like CO2, into useful materials that ultimately will degrade back into CO2,” he said.
Aquaplastic is still being studied and is not ready for broad distribution, Joshi acknowledged. The shift to a commercial product “is a bit unclear right now,” he said, adding that it may depend on securing more funding.
“We make stuff one flask at a time, and we dry the plastic on little molds that we fabricate ourselves,” he said. “Making huge roll-to-roll things is the other end of production that we need to hook up with.”
But Joshi said it is still a potentially better alternative to plastic, which requires the extraction of fossil fuels. According to a report by the Center for International Environmental Law, 8.3 billion metric tons of virgin plastic had been produced by the end of 2015, and about two-thirds of it remains in the environment, since plastic does not biodegrade or could take tens or hundreds of years to do so.
And it comes at a time when the demand for plastic is growing, nearly doubling since 2000 as new applications are discovered, more products are individually packaged, and oil and natural gas, which are used to make plastic, are getting cheaper, according to the International Energy Agency. It is expected to double again by 2040, according to the World Economic Forum.
Jeffrey S. Moore, a professor of chemistry at the University of Illinois who was not affiliated with the study, said that there are some big barriers to making aquaplastic scalable and competitive with traditional plastic.
It is currently not water-resistant, for example. Customers expect plastic packages to offer protection for their food or other sterile objects, Moore said. At least in this iteration, Moore said, aquaplastic still has a long way to go.
“The investment and potential and the energy cost to get us there to grow things on the timeline and scale of manufacturing that we’re used to seems to be a big hurdle, ” Moore said.
But, Moore said, he is excited about the potential: “I like the idea that biology has pervaded the planet for the last 3 billion years, and so why not find a solution wrapped up in biology to the synthetic problems we’ve created?”
washingtonpost.com, 12 May 2021