Nylon-6, a polyamide polymer (PA6), is widely used in fabrics, ropes, netting, automobile parts, and more. The U.S. annual consumption of PA6 is 0.45 million metric tons (MMT/year), and 5.53 MMT/year globally, yielding 2.9 kg of carbon dioxide (CO<sub>2</sub>) e/kg of net greenhouse gases and 4.1 kg CO<sub>2</sub> e/kg of net total emissions, on par with vinyl acetates and rubber production. PA6 is largely considered recalcitrant and currently only ~5% of total polyamide waste is recycled. Thus, degradation and upcycling technologies are needed for this ubiquitous polymer. Enzymatic degradation mechanisms are of interest due to low cost and tunability. However, to date, few groups have reported PA6 degradation using enzymes or microbial consortia. The few studies that exist show promise for several strains and enzymes, but the degradation mechanism has not been elucidated. We utilized promising enzymes (fungal peroxidases, cutinases, and proteases) to degrade micronized PA6 powder, in addition to incubating several fungal and bacterial strains and consortia with PA6. Our results demonstrate weight loss using cutinases and fungal peroxidases, and generation of PA6 monomers caprolactam and 6-aminohexanoate in protease incubation experiments. Thus, these enzymes show great potential as candidates for PA6 degradation to monomeric compounds. Further, our incubations with environmental consortia yielded decreases in 6-aminohexanoate, indicating the potential for nylon hydrolases to be present that may also be capable of degrading oligomeric PA6 constituents. Our results yield promising tools for the degradation of PA6, which may be improved with synthetic biology tools and combined with upcycling techniques to promote advances towards a circular plastics economy.

Degradation of nylon-6 with enzymatic and microbial consortia

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.