The discovery of new metagenomic urethanases utilising a novel colorimetric assay for applications in the biodegradation of polyurethanes

The enzymatic molecular recycling of plastics is of increasing interest, where polymers are converted into monomers for reuse or upcycled into value added chemicals. Polyurethanes are an important class of synthetic hydrolysable polymers found in textiles as an elastane component, also known as lycra and spandex, with most post-consumer waste currently disposed of in landfill. Here we have identified three active novel urethane hydrolytic enzymes from a drain metagenome able to breakdown methylenedianiline-based elastane model substrates. In addition, we have established a new colorimetric assay, suitable for high-throughput applications using tyrosinases. For the urethanases identified, the reaction conditions and substrate scope were explored. Finally, the urethanases and assay were used with commercial fabrics, demonstrating breakdown of the polymer.