A biodiesel byproduct generated by the bioenergy industry could provide a greener pathway for nylon production, after researchers developed a microbial platform capable of converting glycerol into key raw materials used to manufacture nylon.
The breakthrough was achieved by a research team led by Distinguished Professor Sang Yup Lee from the Department of Chemical and Biomolecular Engineering at the Korea Advanced Institute of Science and Technology (KAIST). The findings were published in the Proceedings of the National Academy of Sciences, Phys.Org reported.
Nylon is widely used in products ranging from clothing and packaging films to automobiles and industrial machinery. However, the raw materials needed to produce nylon are traditionally derived from fossil fuels, resulting in significant carbon emissions.
The researchers engineered strains of Escherichia coli to produce adipic acid, hexamethylenediamine and epsilon-caprolactam, three important monomers used in the production of nylon 6,6 and nylon 6. The process uses glycerol, a renewable carbon source generated during biodiesel manufacturing.
The team designed a modular system in which different E. coli strains performed separate tasks. One strain converted glycerol into adipic acid, while another transformed adipic acid into either hexamethylenediamine or epsilon-caprolactam.
Using this integrated approach, the researchers successfully produced all three nylon precursors within a single platform.
To improve efficiency, the team tested and optimized various enzymes involved in the production pathway. For epsilon-caprolactam production, researchers also developed a fusion enzyme designed to enhance reaction efficiency through improved cofactor regeneration.
In addition, artificial intelligence was used to improve the performance of key enzymes in the upstream production pathway, helping increase adipic acid output.
The process achieved adipic acid production of 6 grams per litre during fed-batch fermentation. By applying a delayed inoculation strategy, in which microbial strains are introduced at different stages rather than simultaneously, the researchers produced 230 milligrams per litre of hexamethylenediamine and 808 micrograms per litre of epsilon-caprolactam using only glycerol as the feedstock.
Although production levels remain relatively low for commercial applications, the team said the results represent some of the highest reported performances for direct glycerol-based production of these compounds.
The researchers believe the technology demonstrates the potential to replace petroleum-based nylon feedstocks with renewable alternatives and could contribute to more sustainable manufacturing of plastics and synthetic materials.
Professor Lee said the study establishes a modular microbial platform capable of producing essential nylon monomers from renewable carbon sources. He added that future work will focus on combining artificial intelligence-based enzyme design with advanced metabolic engineering techniques to boost production levels and expand the platform for manufacturing a wider range of bio-based polymer materials.
