Breaking Down Plastics Using Enzymes
- Yasmin Prabhudas
- 3 days ago
- 6 min read
Company Discovers Microbe with Potential Plastic-Degrading Enzymes
The world relies on plastics for endless beneficial uses, but alarming amounts of plastic waste are polluting oceans and waterways, and there’s growing evidence that microplastics are showing up in millions of human bodies. And, because many plastics are built to last, they can take decades or even centuries to disintegrate. The seriousness of the problem has been underscored by the United Nations Environment Programme, which chose to put a focus on ending plastic pollution globally, as the theme for this year's World Environment Day.
In the face of growing concerns about plastic waste, a pressing research question is how to break down these plastics so they are no longer harmful.
Some scientists are carrying out research to see if enzymes could play a key part in doing that job. An example is a Boston-based company called Breaking, which has taken up the mission to find a quick way to break down plastics. It has discovered a microorganism that looks promising—even a “game-changer”—in this quest.
Plastic Waste Exploding
Global plastic waste has more than doubled from 156 million tons in 2000 to 353 million tons in 2019, according to the Global Plastics Outlook report, published by the Organization for Economic Cooperation and Development (OECD) in 2022.
Not surprisingly, the growth in plastic waste stems from the massive escalation in plastic production worldwide—it rose from 234 million tons in 2000 to 460 million tons in 2019.
The OECD estimates that 22 million tons of plastic was released into the environment in 2019 alone. The majority—88%—consisted of macroplastics, arising as a result of poor collection and disposal facilities, while 12% was comprised of microplastics (smaller than 5 millimeters or close to 0.2 inches in diameter) resulting from, for example, tire abrasion or washing textiles.
Meanwhile, the OECD claims some 109 million tons has already accumulated in rivers and 30 million tons in the sea.
The presence of microplastics in the environment poses significant risks to human health and fragile ecosystems. The UN Environment Programme states that microplastics can enter the human system when inhaled or ingested, and they have been shown to have entered the food chain. They have been found in all parts of the human body, including in artery walls.
Microplastics can slow the growth of phytoplankton, while plastics entering the marine environment can have a devastating effect on animals, birds, and fish by entangling them, lacerating internal tissues, and causing toxic harm.
Microplastics can slow the growth of phytoplankton, while plastics entering the marine environment can have a devastating effect on animals, birds, and fish by entangling them, lacerating internal tissues, and causing toxic harm.
All of these unwanted outcomes are prompting scientists to find ways to break down or neutralize these plastics. Research with enzymes has emerged as a promising new approach.
What Are Enzymes?
Enzymes are usually proteins (structures composed of amino acids) or ribonucleic acids (molecules that are made up of nucleotides and are present in most living things). They speed up chemical reactions to carry out different functions in all living beings and are vital parts of any organism.
In humans, enzymes in saliva—amylase and lipase—break down sugars and fats, while protease in the stomach makes sure proteins are digested. Enzymes turn starch into small molecules. Meanwhile, pepsin breaks down proteins from food in the stomach. They are decomposed further in the small intestines and turned into amino acids and eventually removed from the body following reactions in the liver.
In the natural world, enzymes break down and build molecules and accelerate biological processes. The stomachs of herbivorous creatures, for example, use the enzyme cellulase to digest plant cellulose into smaller-molecule nutrients.
Scientists are looking into whether enzymes could be used in a similar way to break down plastics.
Scientists are looking into whether enzymes could be used in a similar way to break down plastics. Such a development could prove to be a new way of dealing with the material in addition to those already available, such as through chemical upcycling [see The Earth & I, “From Bags to Riches—Upcycling Plastic into Viable Products”].
In fact, in 2016, Japanese researchers discovered a bacterium (Ideonella sakaiensis) that can break down PET plastic through two enzymes. Another species (Comamonas testosteroni) was found in 2024 by Northwestern University researchers also to have an enzyme that can break down PET.
Discovering a New Microorganism and Its Enzymes
In Boston, the team at Breaking has discovered that a microorganism, dubbed Microbe X-32, has the potential to speed up the breakdown of plastics, beyond PET, that are hard to degrade.
“We discovered the microorganism, X-32, which is very interesting because it can survive off or grow on plastics that are very commonly known to be hard to degrade,” say Breaking co-founders CEO Sukanya Punthambaker, PhD, and chief scientific officer Vaskar Gnyawali, PhD. “What we are doing right now is understanding the mechanism of this degradation and using biotechnological tools to improve it.”
Plastics that could potentially be broken down are major ones, such as polyolefins, polyesters, and polyamides, which microbes have never been able to degrade without the plastics first being treated. “We have discovered potential plastic-degrading enzymes from our microbe that could break down these tough polymers.”
Gnyawali adds that the enzymes can be engineered to ensure optimal performance. “The enzymes become super enzymes when we engineer them to speed up the process,” he explains. “Unless we engineer them, they are not efficient enough or [cannot] degrade plastics in the timeline we want, such as weeks, days, or even hours.”
“The enzymes become super enzymes when we engineer them to speed up the process. Unless we engineer them, they are not efficient enough or [cannot] degrade plastics in the timeline we want, such as weeks, days, or even hours.”
When the microbe interacts with the polymer chains, the end product is likely to consist of innocuous substances, such as water, carbon dioxide, and biomass.
However, there are limitations. For instance, an individual microbe will not be able to break down all types of plastic.
“There are hundreds of different types of plastics, and each of these plastics requires different degradation processes,” Gnyawali says. But he and the Breaking team are still optimistic—they are discovering new organisms and microorganisms, which they believe could be used to degrade a multitude of plastic types.
Multiple Applications
Breaking’s technology has the potential to be applied across a range of settings. For example, microbes and their enzymes could break down plastic contaminants that are assimilated in anaerobic digestion plants. They can also promote biogas and biomass production through degrading plastic efficiently—and treat wastewater that contains microplastics before it goes back into the environment.
They could further break down plastics that have contaminated soil through agriculture, remediate soil tainted by plastics from industrial facilities, or degrade plastics on landfill sites and at treatment plants. In addition, they could be used to break down plastics that are in the ocean through a “collect and degrade” initiative.
The technology could accelerate the breakdown of items such as rubber boot soles (with a natural decomposition time of 40 to 80 years), fishing line (600 to 650 years), and plastic bottles (450 to 1,000 years). This would help prevent buildup in landfills, oceans, and other ecosystems, ensuring that wildlife and the environment are protected.
Minimizing Impact
But does the process of degrading plastics in this way itself come with a carbon footprint? Using enzymes is more sustainable, safe, and energy efficient than using chemical catalysts, as no byproducts are produced. This means there is no need for waste to be treated and there is no pollution. Enzymes are biodegradable and nontoxic, and their processes are mainly performed in water.
Using enzymes is more sustainable, safe, and energy efficient than using chemical catalysts, as no by-products are produced.
Gnyawali confirms that the use of enzymatic processes themselves does not present environmental challenges. But the company tries to make sure its research is carried out in a way that reduces carbon dioxide emissions by minimizing waste, which means using “mild processes” through “green chemistry.”
Paul Anastas and John Warner, who developed a framework for green chemistry, have defined it as “the utilization of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture, and application of chemical products.”
Warner is on Breaking’s scientific advisory board.
Looking to the Future
Punthambaker and Gnyawali believe the potential of enzymes in the fight against plastic pollution is huge.
“It will be a game changer,” Gnyawali says, “if we can get these enzymes to work on the scale that we want, if we can engineer and optimize enzymes to the functions that they can decrease these plastics in the time scale that we want—days or weeks—because naturally they don’t degrade in years, decades, or hundreds of years.”
*Yasmin Prabhudas is a freelance journalist working mainly for nonprofit organizations, labor unions, the education sector, and government agencies.
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