2024 AIChE Annual Meeting

(719a) Invited Talk: Enzymatic Nylon Synthesis and Hydrolysis

Author

Michener, J. - Presenter, Oak Ridge National Lab
Polyamides are important natural and synthetic polymers, exemplified respectively by proteins and nylons. Chemical synthesis of polyamides is highly efficient, but also energy-intensive and non-selective and therefore requires pure substrates with near-perfect stoichiometry. Similarly, chemical recycling is energetically costly and typically requires material sorting prior to deconstruction. We are developing enzymatic approaches for polyamide synthesis and deconstruction that leverage substrate- and product-selectivity while simultaneously reducing energy demands.

Proteins achieve their impressive properties through sequence-controlled polymerization of diverse monomers. However, chemical polymerization of multiple monomers yields random copolymers with poor material properties. Controlling the monomer sequence of synthetic polyamides could provide new materials with improved properties. To this end, we have enzymatically synthesized isopeptide bonds between commercially relevant substrates to generate sequenced oligoamide products at high yield. These oligoamides can then be chemically polymerized to form nylon polyamides with complex repeat units and diverse characteristics. Engineering efforts focus on improving enzyme activity and specificity.

Motivated by the challenges of recycling both commodity nylons and these newly synthesized polymers, we have also investigated selective enzymatic nylon hydrolysis. One nylon hydrolase from the Ntn hydrolase superfamily, NylC, had been well characterized. We tested 95 diverse homologs from this superfamily and demonstrated that nylon hydrolase activity is common, occurring in approximately 40% of the tested enzymes. These nylon hydrolases varied in substrate- and product-selectivity, including one enzyme designated Nyl50 that is selective for PA66 hydrolysis compared to PA6. Structural studies are illuminating factors that affect hydrolysis, and engineering efforts are in progress to increase Nyl50 activity and selectivity.

In combination, these efforts provide a route to enzymatic synthesis and hydrolysis of bio-advantaged nylon polymers.