Belgrade, Serbia – With so much waste polyurethane ending up in landfill because of the challenges involved in recycling, strategies to efficiently deal with the waste safely and efficiently are becoming increasingly important. A team at the University of Belgrade has been looking for biocatalysts that might prove more effective, and potentially lead to an effective industrial biodegradation process for PU.
Assessments of PU degradation are typically carried out on Covestro’s aliphatic polyester PU Impranil but, they said, the assays do not give details about the enzymes involved, or whether ester or urethane bonds are being broken. Furthermore, few microorganisms or enzymes have thus far been shown to break urethane bonds.
They therefore synthesised and characterised eight model compounds based on phenyl isocyanate and TDI, representing partial hydrolysis products from PU, that might give a better insight into biodegradation. These were assessed in terms of their toxicity and suitability as substrates for identifying novel biocatalysts that might biodegrade PU.
The compounds were then used to study the mechanism of ester and urethane bond cleavage of several plastic-degrading enzymes. Of the 220 microbial strains they screened, the antibiotic-producing bacterial strain Amycolatopsis mediterranei ISP5501 was shown to degrade various polyether and polyester polyurethanes and, importantly, break the urethane bond in both cases. A genomic analysis was run to identify the enzymes responsible.
They suggest that enzymes from this organism had potential as a starting point for developing an effective biotechnological process for treating PU waste.
The work has been published in the journal Catalysts.
