Scientists from the University of Portsmouth and the University of Manchester say they have developed a fusion enzyme that can help break down polyester fibers in blended textiles, a category of waste that has long resisted efficient recycling. The study, published in Bioresource Technology, reports that pairing the enzyme with optimized plastic preparation methods can help address a persistent bottleneck in processing cotton–polyester fabrics at the high material concentrations that industrial recycling demands. The result is a biological tool that could shift how the textile industry handles some of its most stubborn waste streams.
How the Fusion Enzyme Works
The core advance builds on a well-established two-enzyme system for degrading polyethylene terephthalate, or PET, the polymer that makes up polyester fabric. Two enzymes, PETase and MHETase, work in sequence: PETase clips the long PET polymer chains into shorter fragments, and MHETase then converts those fragments into their original chemical building blocks. Earlier research provided detailed structural and kinetic data on both enzymes, supporting the idea that linking their activities can improve overall depolymerization compared with using either enzyme alone.
The Portsmouth and Manchester team took this a step further by fusing the two enzyme activities into a single protein and pairing it with a binding module that helps the enzyme grip tightly onto solid plastic surfaces. According to a report on the findings, one of the researchers noted that by matching the enzyme with the right binding module and preparing the plastic in the right way, they could overcome a major bottleneck in PET recycling. That bottleneck is straightforward: at the high plastic concentrations needed for cost-effective recycling, enzymes struggle to access enough polymer surface area. The fusion design and tailored pretreatment together solve that access problem, allowing the hydrolase to keep working even as solids loading rises to levels relevant for industrial reactors.
Tackling the Cotton–Polyester Problem
Most discarded clothing is not pure polyester or pure cotton. It is a blend, and that mix creates a recycling headache. Mechanical sorting cannot cleanly separate fibers woven together at the thread level, so blended garments typically end up incinerated or buried in landfills. The new study specifically targets this mixed textile waste of polyester and cotton, using a sequential chemical–enzymatic process. First, the cotton component is separated and converted into microcrystalline cellulose, a material with established commercial uses in pharmaceuticals and food products. The reported conversion rate for cotton to microcrystalline cellulose exceeds 70%. Then the isolated polyester fibers undergo enzymatic depolymerization by the PET hydrolase, yielding monomers that, in principle, could be used to make new PET.
This sequential approach matters because it extracts value from both halves of the blend rather than sacrificing one to recover the other. Earlier work on cotton and PET mixed-fiber recycling, including strategies such as enzyme-displaying spore systems, has explored similar goals, and the new study argues that the fusion enzyme’s ability to operate at industrially relevant solids loading could improve practicality. A separate study published earlier this year argued that high solids loading is important for economically and environmentally viable enzymatic PET recycling, helping explain why performance at elevated plastic concentrations is emphasized in the new work.
Why Pretreatment Is Half the Battle
An enzyme is only as effective as its access to the target material, and polyester textiles present a tougher challenge than PET bottles. Textile fibers are often dyed, coated, or heat-treated during manufacturing, making them resistant to biological breakdown. Recent work published in the Proceedings of the National Academy of Sciences demonstrated that controlled mixing and melt-processing can boost enzymatic depolymerization of recalcitrant or unsortable polyester wastes. The idea is to restructure the plastic’s physical form before the enzyme ever touches it, increasing the surface area available for attack.
The Portsmouth and Manchester study applies a related logic. By optimizing how the polyester substrate is prepared, the team ensures the fusion enzyme can work efficiently even on fibers that would otherwise resist degradation. This is not a minor technical detail. A review in Nature Reviews Bioengineering cataloging the full range of polyester-degrading biocatalysts identified pretreatment requirements, enzyme stability, and solids loading as the three main industrial constraints standing between laboratory results and factory-scale deployment. The authors position the fusion enzyme and process as a step toward addressing these constraints together, compared with earlier proof-of-concept demonstrations.
Industrial players are already investing in better front-end processing for textile waste. A recent announcement from Carbios highlighted a dedicated textile preparation line designed to clean, shred, and condition polyester-rich materials before enzymatic treatment. The academic work on fusion enzymes slots neatly into this emerging infrastructure: if pretreatment can deliver more uniform, accessible fibers, then advanced hydrolases can convert a larger fraction of that feedstock into reusable monomers.
Enzymatic Recycling Is Not the Only Path
Enzymes are not the sole route to breaking down blended textiles. A separate line of research has explored non-enzymatic co-hydrolysis of PET and cotton blends using gamma-valerolactone as a solvent, according to a study in Nature Communications. That chemical approach offers its own advantages, particularly in processing speed and tolerance for contaminated feedstocks, and it can handle mixed fibers without requiring precise biological conditions.
Meanwhile, computational redesign of hydrolase enzymes has achieved nearly complete PET depolymerization at high solids loading in other work reported in Nature Communications, setting quantitative benchmarks for what engineered enzymes can accomplish under industrial conditions. These redesigned catalysts show that carefully tuned active sites and surface properties can maintain activity even when the reaction mixture is crowded with plastic particles.
The tension between enzymatic and chemical approaches is less a competition than a portfolio question. Chemical routes can be robust and fast but may require higher temperatures, specialized solvents, and additional steps to purify recovered monomers. Enzymatic methods typically run at lower temperatures and can offer high selectivity, reducing side reactions and contamination, but they depend on carefully controlled environments and catalysts that remain stable over long operating times. Blended textiles only magnify these trade-offs because any viable process must deal with both natural fibers and synthetic polymers, plus dyes, finishes, and dirt picked up during use.
From Lab Bench to Textile Mills
For now, the Portsmouth and Manchester fusion enzyme remains a laboratory advance, but it is tuned with industrial realities in mind. The ability to function at high solids loading, tolerate realistic textile pretreatments, and integrate into a sequential process that recovers both cotton and polyester moves it closer to commercial relevance. The study’s focus on blended fabrics also reflects the actual composition of most clothing waste, rather than the cleaner, single-polymer streams that have dominated early recycling research.
Scaling up will still require answers to practical questions: how to manufacture the enzyme at low cost, how to maintain activity over repeated cycles, and how to integrate the process into existing textile sorting and processing lines. Partnerships between academic groups and companies building textile preparation facilities suggest that those questions are now being tackled in parallel rather than in isolation.
As clothing consumption continues to rise globally, the pressure to divert blended textiles from landfills and incinerators will only increase. Whether through fusion enzymes, computationally redesigned hydrolases, or solvent-based co-hydrolysis, the emerging toolkit for handling cotton–polyester blends is expanding. The new fusion enzyme does not, by itself, solve the fashion industry’s waste problem, but it demonstrates that carefully engineered biology, combined with smart pretreatment, can unlock recycling pathways for materials once written off as unrecoverable.
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*This article was researched with the help of AI, with human editors creating the final content.
