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High recycling rate in record time

PET Recycling: Biochemists found start-up

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The enzyme PHL7 is making headlines – discovered in a compost heap at Leipzig’s Südfriedhof cemetery, it breaks down PET, such as plastic fruit trays from the supermarket, by more than 90 per cent in a record time of just 16 hours. That is twice as fast as previously known enzymes. This biological PET recycling method helps conserve resources, especially fossil fuels and environmentally harmful energy sources. Drawing on these research findings – which have also been published in academic journals – biochemists Dr Christian Sonnendecker and Dr Ronny Frank from Leipzig University came up with a business idea and recently founded the company ESTER Biotech.

Dr. Ronny Frank und Dr. Christian Sonnendecker stehen vor einem Sack voll kleingehäckselten Plastikteilen.
Dr Ronny Frank and Dr Christian Sonnendecker in front of a sack filled with shredded PET fruit trays, ready to be broken down into their chemical components with the help of the enzyme PHL7. Photo: Swen Reichhold,…

In the lab rooms of researchers Dr Christian Sonnendecker and Dr Ronny Frank at the Centre for Biomedicine and Biotechnology (BBZ) on Deutscher Platz, a newly delivered large glass reactor with a capacity of 100 litres stands ready alongside lab equipment, waiting to be put into operation. In adjacent rooms, sacks of single-use PET plastic trays, previously used by supermarkets to sell fruit, are being stored ready for processing. The reactor will be used to break down the PET into its individual components at a temperature of 65 to 70 degrees Celsius by adding the enzyme PHL7 – all within 16 hours. This is a more efficient system that uses significantly less energy than previous methods, especially when compared to incineration, which releases environmentally harmful emissions.

The reactor currently under construction is significantly larger than the existing one. The volumes of PET involved are increasing, as this method is set to become commercially viable. In addition to the enzyme itself, a key innovation was a novel measuring technique developed by Dr Ronny Frank. “It allows enzymes to be improved more quickly, cost-effectively and based on data. It can generate large, reliable datasets – perfect for machine learning. This made it possible to significantly optimise the enzyme: it now works faster, more stably and more efficiently,” says Frank. 

After their method attracted attention not only within the scientific community but also in the media, the question arose: “What do we do with this now? Let’s start a company!” Encouraged by a friend who had founded the start-up Glashaus 3D with the support of Leipzig University, and by the University’s SMILE start-up initiative, they took part in the Leipzig Start-up Night in 2022 – and won the audience award with their idea. “The public loves the story of the enzyme found in the cemetery that led to the discovery of our process,” says Ronny Frank. From that point on, the idea of founding a spin-off really began to take shape.

With the prize money and support from the University Foundation, the team purchased equipment to further develop their recycling process and investigate how to increase volumes and improve efficiency.

enlarge the image: Zu sehen ist ein Inkubator mit einer Bakteriensuspension. Die Trübheit der Suspension wird optisch überprüft.
The enzyme is produced through fermentation using microorganisms. The cloudiness of the suspension is checked visually. Photo: Swen Reichhold, Leipzig University

Patent research findings before publication

In 2024, the aspiring entrepreneurs received funding from the Development Bank of Saxony (SAB) for a validation study – the first major funding for their budding start-up. “With this funding, we had a year to assess whether our idea could realistically be turned into a viable company,” says Christian Sonnendecker. “Securing funding, writing applications, setting up lab and office space, and recruiting staff all take a lot of time – and that’s while still having to earn a living on the side.” 

But that’s not all when it comes to starting a business: “We’re in regular contact with the Department of Research Services. Among other things, it’s about getting advice and also filing patents,” says Sonnendecker. “You absolutely need someone at your side who understands patent law. The foundation of a business is holding the necessary patents.” And this, he says, requires a shift in thinking for researchers who want to start their own business or move into industry: “For understandable reasons, researchers feel a strong urge to publish their results constantly. But in business, you should only publish your findings once they’ve been patented – that way, you benefit from them yourself, rather than someone else, potentially even a competitor, who might otherwise take and exploit your invention. A basic awareness of legal rights is essential.” To help raise this awareness, Leipzig University’s SMILE start-up initiative and the SEPT Competence Center offer support to spin-offs emerging from the University.  

enlarge the image: Zu sehen sind nebeneinander fünf Gläser, die mit einer Flüssigkeit gefüllt sind. Im linken Glas ist ein größeres Plastikstück, im ganz rechten ist das Plastikstück komplett in der Flüssigkeit aufgelöst. Die Gläser dazwischen zeigen den Zerfallsprozess über einen Zeitraum von mehreren Stunden.
This sequence of images shows how the enzyme PHL7 breaks down a PET tray in a small bioreactor at just 65 degrees Celsius. Aside from the enzyme, only water and a pH buffer are required. Within twelve hours, the tray is…

Rooted in academia, reaching for the market

The young entrepreneurs are currently receiving two years of funding through the EXIST Research Transfer programme run by the Federal Ministry for Economic Affairs and Climate Action. Just a few weeks ago, they founded their company together with two other colleagues: ESTER Biotech GmbH.

At some point, they say, they won’t be able to manage without investors – “at the latest when it comes to large-scale industrial plants,” when their process begins to play a key role in the recycling market. To reach that stage, they’ll also need to invest in marketing and market research. Because the success of their business idea depends on developing something that actually meets market demand: “We don’t make the product – the customer makes the product. The customer asks us: can you do this? Do you offer that? Can your enzymes break down my type of plastic? And we either say yes on the spot, because we know it works, or we investigate whether it’s possible – and if so, how,” explains Ronny Frank. This is done with the support of researchers from Leipzig University, such as the junior research group led by Dr Georg Künze at the Meiler Lab, which is helping to further develop the plastic-degrading enzymes. One of the aims of the now four-person team is to “stay rooted in academia while reaching for the market” – and to continue securing external funding for research, in other words, to remain rooted in the university.  

Marketing is also important: they have a website and YouTube channel, they are on LinkedIn, and they attend specialist conferences – ideally as speakers themselves, to promote their work and seek partnerships.

Dr. Ronny Frank und Dr. Christian Sonnendecker stehen vor einem Computer. Auf dem Monitor sind Fotos vom chemischen Zersetzungsprozess zu sehen.
Ronny Frank steht vor einem Inkubator und stellt die Versuchsanordnung, bestehend aus 48 Messfeldern, die miteinander verkabelt sind, in den Inkubator.

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