Enzyme Breakthroughs

Plastic pollution is one of the most pressing environmental challenges of the 21st century, with microplastics—fragments less than five millimetres in size—permeating oceans, soil and even the air we breathe. As concerns mount over their long-term ecological and health impacts, researchers are turning to a novel solution: bioengineered enzymes capable of degrading these persistent pollutants.

The Microplastics Conundrum

Microplastics originate from two main sources: primary microplastics, intentionally manufactured for products like cosmetics and industrial abrasives, and secondary microplastics, which form from the breakdown of larger plastic debris. Their omnipresence in global ecosystems—detected in deep-sea trenches, Arctic ice and even human blood—has intensified efforts to develop effective remediation technologies.

Traditional methods of plastic waste management, such as incineration, landfilling and mechanical recycling, fall short when addressing microplastics due to their small size and widespread dispersion. With growing evidence linking microplastic ingestion to inflammatory diseases and endocrine disruption, scientists are racing to engineer biological catalysts that can selectively and efficiently degrade these synthetic polymers.

The Enzyme Revolution

In 2016, researchers in Japan discovered Ideonella sakaiensis, a bacterium that evolved to digest polyethylene terephthalate (PET), the polymer commonly used in water bottles and synthetic fibres. The key to its ability lay in two enzymes: PETase and MHETase, which break PET down into its fundamental monomers. This groundbreaking discovery spurred a wave of research into engineering more efficient and versatile enzymes.

One of the most promising developments is the creation of "super-enzymes"—genetically modified variants that degrade plastics at unprecedented rates. Researchers at the University of Portsmouth and the U.S. National Renewable Energy Laboratory have fused PETase and MHETase into a single enzyme, accelerating PET degradation by up to six times compared to natural processes. Meanwhile, Cornell University’s Food Science department is developing enzymes capable of breaking down microplastics in wastewater treatment facilities, targeting a major entry point of plastic pollution into the environment.

Engineering Enzymes for Real-World Applications

Enzyme-based bioremediation offers several advantages over conventional methods. Unlike chemical treatments that may produce harmful byproducts, enzymatic degradation yields benign substances such as water and carbon dioxide. Additionally, enzymes operate under mild conditions, reducing energy costs compared to incineration or mechanical processing.

However, significant challenges remain. Naturally occurring plastic-degrading enzymes often work too slowly for practical application. To overcome this, researchers are using protein engineering techniques such as directed evolution and machine learning to enhance enzyme efficiency. These methods allow scientists to fine-tune enzyme structures, optimising their ability to bind and break down plastic polymers.

In wastewater treatment plants, where microplastics from synthetic textiles, personal care products and industrial sources accumulate, engineered enzymes could serve as a frontline defence. Julie Goddard’s lab at Cornell is exploring enzyme variants that function effectively in the harsh conditions of sewage sludge, an environment rich in organic matter and fluctuating pH levels. Their goal is to integrate these enzymes into existing filtration systems, ensuring microplastics are broken down before they enter agricultural irrigation or drinking water supplies.

Scaling Up: From Lab to Industry

While laboratory results are promising, deploying enzymatic plastic degradation at scale remains a logistical hurdle. Producing sufficient quantities of engineered enzymes at low cost is critical for widespread adoption. Companies exploring commercial applications are experimenting with enzyme immobilisation techniques, which tether enzymes to solid supports, enhancing their stability and reusability.

French startup Carbios has made significant strides in this space, pioneering an industrial enzymatic recycling process for PET plastics. By harnessing engineered enzymes, the company has achieved near-complete depolymerisation of PET waste within hours—a feat that traditional recycling methods struggle to match. As the technology advances, similar approaches could be applied to tackle microplastics across diverse environments, from wastewater treatment to ocean cleanup initiatives.

The Future of Enzymatic Plastic Remediation

The race to engineer enzymes capable of breaking down microplastics is more than an academic pursuit—it represents a critical frontier in the fight against global plastic pollution. Governments and private investors alike are recognising the potential of enzyme-based solutions, with funding initiatives aimed at accelerating research and commercialisation.

As breakthroughs continue to emerge, the fusion of biotechnology and environmental science may soon redefine our approach to one of the planet’s most pervasive pollutants. Enzymatic degradation could transform plastic from an enduring environmental hazard into a recyclable, circular resource—a vision that once seemed distant but is now within reach.