# Polyurethane Cascade Depolymerization by a Combination of Thermal Pretreatment and Enzymatic Hydrolysis

## TL;DR

The paper presents a new method to break down polyurethane plastics using heat and enzymes, improving the recovery of valuable materials.

## Contribution

A novel cascade process combining thermal pretreatment and enzymatic hydrolysis is introduced for efficient polyurethane depolymerization.

## Key findings

- Thermal pretreatment increased weight loss of polyurethane films from less than 2% to over 8% after enzymatic treatment.
- Combining cutinase HiC and urethanase SP2 in a cascade improved monomer recovery by nearly threefold compared to SP2 alone.
- HiC variants degraded polyurethane faster, achieving significant degradation within 24 hours.

## Abstract

Enzymatic depolymerization of postconsumer polyurethanes (PURs) offers a promising route for sustainable plastic waste management. However, the complex chemistry of PURs containing carbamate, ether, and ester bonds poses a challenge for such a biotechnological process. Here, we explored the deconstruction of a commercial polyether‐polyester‐PUR through a cascade depolymerization approach, in which a low‐temperature thermal pretreatment (180°C, 4 h) was combined with tandem enzymatic hydrolysis. Heat treatment modified the polymer's physicochemical properties, enabling the cutinase HiC from Humicola insolens to cause more than 8% weight loss of the treated PUR films, versus less than 2% of the untreated control after 48 h incubation. Furthermore, the addition of the metagenomic urethanase SP2 completed the one‐pot enzymatic cascade, achieving not only depolymerization to the constituent monomer, 4,4′‐methylenedianiline (MDA), but also a nearly 3‐fold increase in MDA yield compared to using SP2 alone. Docking studies highlighted HiC's specificity toward ester bonds in the PUR polymeric units, and two HiC variants further enhanced degradation within 24 h. Altogether, this work lays the foundation for future investigation and process design for the depolymerization of polyether‐polyester‐PURs and related materials by cascade enzymatic reactions.

This study explored the cascade depolymerization of a polyether‐polyester polyurethane based on a combination of low‐temperature thermal treatment and enzymatic hydrolysis. Heat pretreatment changed the physicochemical properties of polyurethane, followed by cutinase‐catalyzed hydrolysis, leading to an increase in weight loss and the production of two intermediates, which were further hydrolyzed into the constituent monomer, 4,4′‐methylenedianiline (MDA) by the urethanase SP2.© 2026 WILEY‐VCH GmbH