Fascination With Technology Produce Nylon Raw Materials from Styrofoam

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Universität des Saarlandes

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In our "Fascination with Technology" section, we present impressive research and development projects to engineers every week. Today: how bacteria produce the raw materials for nylon from harmful polystyrene.

It still sounds a bit like science fiction, but it actually works: bacteria that process environmentally harmful substances like polystyrene to produce the raw materials for nylon without the need for new petroleum. This is exactly what Christoph Wittmann, Professor of Biotechnology in Saarbrücken (Germany), and his colleagues from neighboring disciplines have achieved. How it works in detail has been published in the Chemical Engineering Journal.

Environmentally Friendly Recycling of "problematic" Polystyrene

Plastic waste is not all the same. While one type of plastic can be excellently recycled, another can present significant challenges. "Polystyrene is such a problem child," explains Christoph Wittmann. The professor of systems biotechnology at Saarland University has devoted his entire research career to the question of how certain plastics can be disposed of or recycled in an environmentally friendly way.

The "problematic" polystyrene, whose most well-known form is styrofoam, familiar to everyone, could now lose its status thanks to his work and that of his colleagues and perhaps even become a highly sought-after raw material for basic chemistry.

22 Million Short Tons of Polystyrene Waste

Each year, a staggering 22 million short tons of polystyrene waste are generated worldwide, only a small portion of which can be recycled. However, if Christoph Wittmann has his way, this could soon become a thing of the past. Together with polymer chemists from Professor Markus Gallei's research group, material scientists from the Leibniz Institute for New Materials (INM) in Saarbrücken, and additional partners from Dortmund and Vienna, the biotechnologist from Saarland succeeded in getting bacteria to break down the molecular building blocks of Styrofoam and convert them into useful chemicals. The necessary building blocks were previously extracted from Styrofoam waste using an energy-efficient process—thus laying the foundation for microbial processing.

Manipulate Bacteria Finely And Precisely Over Years

Simply put, of course. As one might guess, you can't give a bacterium of the species *Pseudomonas putida* a stern lecture with a wagging finger. Instead, years of meticulous lab work are required to fine-tune the bacterium's metabolism so that it not only develops an appetite for Styrofoam building blocks (as most bacteria don't naturally enjoy such substances) but is also motivated to excrete useful substances as a "digestive product."

Valuable Raw Materials Thanks to Biological "Upcycling"

Such substances include muconic acid, which can be further split into adipic acid and hexamethylenediamine. "And these two each have six carbon atoms and two acid or amino groups," explains Christoph Wittmann.

Chemists will take notice because: "These are the two components needed for nylon production," explains the scientist. And nylon, in turn, plays a pivotal role in the world of plastics. Countless everyday items contain nylon, including the famous nylon stockings, as well as carpets, car seats, and even kitchen utensils, cable ties, and dowels. It becomes clear: through biological "upcycling," hard-to-recycle polystyrene is transformed into a valuable raw material for high-quality technical and even high-performance plastics—a true advantage compared to traditional "recycling."

The key is that our colleagues were able to prove that the substances obtained through our process have the same properties as those newly produced in the factory using petroleum.

Prof. Dr. Christoph Wittmann, Saarland University

Material Properties Convince

With the process from Saarbrücken, which was developed thanks to funding from the EU project "Repurpose," entirely new approaches are now emerging for the chemical industry to keep the many millions of tons of polystyrene waste in the material cycle and derive new raw materials from it.

"The key is that our colleagues from the INM, led by Aránzazu del Campo, were able to prove that the substances obtained through our process have the same properties as those newly manufactured in factories using petroleum," says Christoph Wittmann. The material properties of plastics derived from recycled polystyrene are therefore identical to those of factory-new plastics. This is important, for example, for the durability of products. They perform just as well as products made from "fresh" petroleum.

Sustainability Requires Interdisciplinary Teams

The researchers were able to gain their insights thanks to the close collaboration and short distances on the Saarland University campus. "This is a unique aspect here in Saarbrücken," explains the biotechnologist. Today, no scientist can achieve success working alone in isolation, particularly in his field. "Sustainability requires interdisciplinary teams," he says. "It can't be done alone."

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