Leipzig University: Enzymatic PET Recycling Becomes Ready for Industrial Use

Building on decades of expertise at the Leipzig University, this research addresses a key challenge in the circular economy: the sustainable recycling of plastics. Using new bioinformatics approaches and interdisciplinary methods, researchers at the Leipzig University have paved the way for a practical, environmentally friendly recycling technology.

The enzyme PHL7 was modified so that it can break down PET plastic more quickly and under industrial conditions. The improved variant R4M10 demonstrated significantly higher degradation performance in the bioreactor than comparable enzymes by breaking down PET into its basic components, ethylene glycol and terephthalic acid. The enzyme PHL7, first isolated from a compost sample from Leipzig’s Südfriedhof cemetery, is considered one of the few naturally occurring hyperactive PET-degrading enzymes. However, it has previously been too unstable and not active enough for technical applications — especially under real-world industrial conditions. The current study now overcomes these hurdles: “Using bioinformatic predictions, we introduced targeted mutations into the amino acid sequence, which led to significantly improved variants. These exhibit increased stability, higher activity, and reduced dependence on salt concentrations — a decisive advantage, as the enzyme now also functions in ordinary tap water,” explains Dr. Georg Künze from the University’s Medical Faculty.

For the experimental work on the study, the research group utilized a variety of modern methods from the summer of 2022 through mid-2025: X-ray crystallography enabled three-dimensional structural analysis, impedance spectroscopy provided real-time data on the reaction process, and molecular dynamics simulations helped decipher the enzymatic degradation at the molecular level. The enzyme variants were tested in stirred reactors under conditions similar to those in industrial settings—with promising results. The findings have already been incorporated into a patent application.

“The developed PHL7 variants are now genuine candidates for industrial application,” emphasizes Dr. Christian Sonnendecker of the Faculty of Chemistry. ESTER-Biotech, a startup founded in Leipzig in 2025 and a spin-off of the Leipzig University, is already planning to scale the technology up to a pilot plant. In the long term, enzymatic recycling could help make the plastics industry more circular and sustainable. The project is not yet complete: further optimizations using artificial intelligence are planned, as is the development of enzymes for other biodegradable plastics such as PLA and PBS. Whether the technology is economically viable will become clear in the coming years and depends not only on technical but also on economic factors.

More than 20 years ago, Prof. Dr. Wolfgang Zimmermann at the Leipzig University was one of the pioneers in the field of plastic-degrading enzymes, with the goal of recycling plastics such as PET under environmentally friendly conditions. With the current study, the field of research has taken a step closer to this goal.