Nylon is one of the world’s most widely used synthetic materials, but producing it still relies heavily on fossil fuels and energy-intensive industrial processes. Researchers now believe there could be a cleaner alternative. 

In a new study published in Nature, scientists describe a technique that converts lignin – a tough, woody component of plants that is often discarded or burned – into adipic acid, one of nylon’s key chemical building blocks. The approach combines refinery-inspired chemical processing with specially engineered microbes that carry out highly selective reactions. 

According to the researchers, the hybrid system delivers a significantly higher yield of adipic acid than previous lignin-based methods, potentially paving the way for a more sustainable and lower-carbon route to nylon production.

New value in a long-ignored industrial byproduct

Often treated as little more than industrial waste, lignin is the natural polymer that gives plants their strength and rigidity. It is one of the most abundant organic materials on the planet and is believed to be the largest underused component of biomass. Every year, millions of tons of lignin are generated as a byproduct of the paper and biofuel industries, with most of it simply burned as a low-value source of energy.

Yet lignin contains a wealth of carbon-rich aromatic structures that could be converted into valuable industrial chemicals. The challenge has been finding an efficient and cost-effective way to break it down into simple, high-value compounds at commercial scale. Researchers have long struggled because lignin-rich byproducts are typically complex, inconsistent mixtures that are difficult to process and refine.

Although lignin has long been seen as a promising renewable source of aromatic chemicals, its complex and highly variable structure has limited its industrial use. The researchers note that lignin often degrades during extraction, while most current processing methods produce complicated mixtures of chemical compounds rather than simple, high-value molecules suitable for large-scale manufacturing.

These limitations mean that current lignin conversion techniques usually achieve yields of only around 20% for any single product, making them commercially unattractive. They also tend to generate complex mixtures of phenolic compounds that are difficult to separate and refine. A more efficient way to convert lignin into adipic acid or other nylon precursors could help reduce both biomass waste and the carbon footprint associated with petroleum-based plastics.

Hybrid chemical and biological process could transform nylon manufacturing

The new approach could help transform low-value plant waste into a key ingredient for nylon production by combining established chemical processing with engineered bacteria. The process begins with poplar wood chips, from which lignin is extracted and broken down into an oil rich in aromatic compounds. 

This oil is then treated in a reactor that removes unwanted oxygen-containing groups, followed by another chemical step that converts it into water-soluble aromatic acids. Finally, engineered microbes complete the process by turning these intermediates into adipic acid.

The researchers then introduced an engineered bacterium, Pseudomonas putida, which converts most of the aromatic carboxylic acids in the mixture into muconolactone. This intermediate can then be chemically transformed into adipic acid, a key component in nylon production.

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