Innovation

Future of Plastics: Eating Away at Plastic Waste

In this installment of the Future of Plastics series, learn how a bioengineered super enzyme is eating away at plastic waste.

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In 2016, just outside a bottle recycling facility in Osaka, Japan, a group of scientists discovered something extraordinary—a plastic “eating” bacteria. This type of bacteria uses plastic as its source of carbon, oxygen and nitrogen.

Unbeknownst to them, this discovery would spark a new flame for scientists aiming to revolutionize the way we eliminate plastic waste.

A new way to eat away at plastic waste

The original bacterium, Ideonella sakaiensis, was able to consume polyethylene terephthalate (PET), the type of plastic most commonly found in bottles. However, researchers noted that the pace at which the bacteria ate through waste was too slow to provide a panacea for plastic waste in the environment.

In 2020, a group of German researchers from the Helmholtz Centre for Environmental Research discovered another bacteria, known as Pseudomonas putida, in the soil just outside a landfill. The lead scientist Dr. Christian Eberlein said that the bacteria has “solvent-tolerance and is one form of extremophilic microorganisms” – meaning it comes from a strain of bacteria that are well-known for their tolerance of organic compounds and other forms of stress. This gives the bacteria the unique ability to digest plastic.

These bacteria were “eating” polyurethane diol, the plastic most commonly used to protect against corrosion, such as shoe soles, artificial heart valves, and electrical equipment. The complex, crystalline structure of polyurethane makes it incredibly difficult to break down, but Pseudomonas putida can do so. Upon discovery, researchers realized they could revolutionize the way we view waste management by accelerating its evolution and bioengineering the bacteria to consumer plastic at a faster pace.

Creating a ‘super enzyme’

Later in 2020, a team of researchers at the University of Portsmouth in the United Kingdom began bioengineering these bacteria into one species so that it could increase degradation speeds by six fold. The resulting “super enzyme” degrades plastic in a matter of days, opening up a world of possibilities for waste reduction.

John McGeehan, director of the Centre for Enzyme Innovation at the University of Portsmouth, agrees that the latest development represents a huge step towards reducing plastic pollution. He states, “this is a trajectory towards trying to make faster enzymes that are more industrially relevant. But it’s also one of those stories about learning from nature, and then bringing it into the lab.” McGeehan’s lab works with an enzyme known as PETase, which splits certain chemical bonds (esters) in PET, leaving smaller molecules that are more easily digestible for the bacteria.

The PETase in this super enzyme breaks down PET and polyurethane into their monomer forms, allowing them to be recycled and rebuilt to form entirely new plastics. Though the bacteria that use PETase have only recently been engineered to survive on plastics, more research is being done to understand the potential of this technology. Researchers could also engineer optimized forms of the “super enzyme” by manipulating its active parts and maximize it’s potential for commercial use.

Closing the loop

These scientific breakthroughs could help us move away from a linear economy and towards a circular one—a transformation which ensures that products can be recycled without degradation of properties, and existing environmental challenges.

PETase and other groundbreaking bacterial discoveries are providing new potential for researchers and industry on how to more sustainably recycle plastics. Although not yet a silver bullet for plastic waste, these bacteria and “super enzymes” have a lot of potential, such as addressing microplastics in water treatment plants, or by developing better and more efficient catalysts used in advanced recycling.

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