Near-complete depolymerization of polyesters with nano-dispersed enzymes

Area of Science:

• Biocatalysis and Polymer Science
• Materials Science and Engineering
• Environmental Science and Sustainability

Background:

• Interfacing enzymes with polymers allows for controlled plastic modification and degradation.
• Previous methods like embedding enzyme microparticles accelerated degradation but compromised material properties and led to microplastic formation.
• Controlled biocatalysis in solid matrices with macromolecular substrates is crucial for effective enzyme-polymer interactions.

Purpose of the Study:

• To develop a method for controlled, programmable degradation of semi-crystalline polyesters using nanoscopically dispersed enzymes.
• To achieve processivity with enzymes, including those with surface-exposed active sites, through engineered enzyme-protectant-polymer complexes.
• To explore the potential of embedded oxidases in polyolefins for material modification.

Main Methods:

• Nanoscopic dispersion of enzymes with deep active sites within semi-crystalline polyesters.
• Engineering enzyme-protectant-polymer complexes to achieve processivity with surface-exposed enzymes.
• Depolymerization of poly(caprolactone) and poly(lactic acid) in soil composts and tap water.
• Embedding oxidases in polyolefins to assess their activity and interaction.

Main Results:

• Nanoscopic enzyme dispersion enabled chain-end-mediated processive depolymerization of polyesters with programmable latency and material integrity.
• Poly(caprolactone) and poly(lactic acid) with <2 wt% enzymes depolymerized in days, achieving up to 98% conversion to small molecules.
• Embedded oxidases in polyolefins retained activity, but hydrocarbon polymers showed poor association with enzymes, limiting chemical modification.

Conclusions:

• Nanoscopic enzyme dispersion offers a viable strategy for controlled polyester degradation, minimizing microplastic formation and facilitating complete conversion to small molecules.
• Enzyme-protectant-polymer complexes can enable processivity for surface-active enzymes, broadening the scope of biocatalytic polymer modification.
• Further research in solid-state enzymology is needed to address challenges with chemically inert substrates and ensure environmental safety.