Discover how evolutionary microbiology turns PET waste into drugs, thanks to a historic chemical reaction “transplanted” into E. coli cells

by Marco Arezio

In the collective imagination, plastic recycling is often limited to the reuse of bottles or the mechanical transformation of materials. But scientific innovation is redefining this scenario, paving the way for radically new processes that exploit the power of synthetic biology. In this context, one of the most surprising discoveries of recent years was born: the integration of Lossen rearrangement, a chemical reaction historically “impossible” to replicate in biological systems, inside living E. coli cells to transform PET plastic waste into high-value molecules such as paracetamol.

This revolution is born from a fundamental question: is it possible to overcome the limits of nature itself, importing into the living world chemical reactions that, until yesterday, belonged only to the most advanced laboratories? The affirmative answer translates into a disruptive potential for the bioeconomy and the circular economy.

What is Lossen Rearrangement and Why is it Revolutionary?

Lossen rearrangement is a chemical reaction discovered in the 19th century, but never integrated into the metabolism of living organisms until today. In traditional laboratory conditions, this reaction allows the transformation of hydroxamic esters into amines through the formation of isocyanate intermediates: an elegant sequence but typically not very compatible with biological systems, due to the drastic conditions required, such as the use of metal catalysts or anhydrous environments.

The real revolution is that, thanks to an ingenious experimental design, this reaction has been transferred for the first time into E. coli cells, making it in fact “biocompatible”. This is an achievement that pushes the boundaries of biochemistry and opens new perspectives for the sustainable synthesis of compounds of great industrial and pharmaceutical interest.

The Breakthrough: Phosphate Catalysis in E. coli

Making Lossen rearrangement possible in a living cell required a simple yet brilliant strategy. Scientists deprived E. coli cells of their natural ability to produce para-aminobenzoate (PABA), a precursor essential for their growth, thus “forcing” them to survive only if they were able to utilize a new external source: a hydroxamic ester derived from PET.

Inside the cell, the catalyst is not a toxic metal, but the very common inorganic phosphate, absolutely compatible with life. It is precisely the phosphate that triggers the Lossen rearrangement, allowing the conversion of the plastic substrate into PABA, which reactivates the growth and vitality of the bacterial colony. This is the demonstration that such an exotic reaction can enter the metabolic language of cells, becoming a crucial step in new production pathways.

From Plastic to Medicine: Molecular Cunning

The heart of this revolution is the direct connection between PET, one of the most widespread and problematic plastic wastes in the world, and the production of paracetamol, a universal drug. Starting from post-consumer PET, the material is converted through a few chemical steps into a hydroxamic ester (called PET-1), ready to be taken up and transformed by E. coli cells.

But the chain does not stop there. By integrating two additional enzymes, one fungal and one bacterial, scientists have managed to biologically complete the last phase of the synthesis: PABA becomes paracetamol, all within a single fermentation and at room temperature, without the need for energy-intensive or polluting chemical processes.

Performance and sustainability

The results achieved are impressive: in less than 48 hours, the conversion yield reaches 92% on purified substrates and exceeds 80% starting from real PET waste. These numbers underline the efficiency of a solution that, in addition to valorizing waste, drastically reduces energy consumption, eliminates the use of harmful catalysts and limits the environmental impact of pharmaceutical production.

The key lies in the integration of biology and chemistry: the reaction occurs in mild conditions, completely compatible with cellular life and in the absence of toxic agents, offering a scalable model for the future of advanced recycling and the production of high-value compounds.

Challenges and application perspectives

Like any radical innovation, this one also brings with it some challenges that still need to be addressed. First of all, the need to optimize the initial degradation of PET, so that the transformation can take place entirely inside the cell without external steps. This step represents the next goal of research, to achieve a true “one-pot” biological recycling.

Another challenge is scalability: the transition from lab to industry will require new genetic engineering strategies and fermentation processes, so as to integrate paracetamol production into existing waste treatment streams. However, the potential of this discovery goes far beyond the single drug: the Lossen rearrangement platform can be adapted to other aromatic compounds and active ingredients, further expanding the impact on the circular economy.

Impact on circular economy and biotechnology

What emerges from this work is a new paradigm: plastic waste, from an environmental problem, becomes a strategic resource for the production of complex and indispensable molecules. The synergy between evolutionary microbiology and synthetic chemistry opens the way to a generation of low-impact production processes, with economic and social benefits that are reflected throughout the industrial chain.

This model represents the first concrete example of “molecular upcycling” carried out directly inside living organisms, in line with the most advanced principles of the circular economy: reduction, reuse and valorization of waste, for a more sustainable and resilient society.

Conclusions

The realization of a biocompatible Lossen rearrangement in E. coli cells marks a milestone in materials science and green chemistry. It is not only a technical achievement, but a change of perspective: it shows how it is possible to overcome natural limits by integrating the best of traditional chemistry with the extraordinary adaptive capacity of living beings.

From today, the prospect of transforming plastic waste into essential medicines such as paracetamol is no longer a utopia, but an increasingly concrete horizon. And this could revolutionize, in the coming years, not only the way we recycle plastic, but also the very concept of chemical production, orienting it definitively towards sustainability and respect for the planet.

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