Nanjing, China – Very few microbial species that produce enzymes capable of efficiently degrading polyurethanes are known, and this is a significant barrier to implementing the biodegradation of waste PU on a large scale Now, scientists at Nanjing Agricultural University have discovered a new PU-degrading bacterium in a coastal mudflat that could have potential for PU foam.
They found the strain by screening samples collected from coastal mudflats. In all, 11 strains were isolated based on their ability to create transparent zones on plates made from Covestro’s Impranil DLN anionic aliphatic polyester PU dispersion.
The most effective strain, the wild-type Aeromicrobium species LTX1, proved particularly efficient at degrading PU foam in an assay. They then used UV mutagenesis to create a strain, MLTX1, that has even greater degradation efficiency.
The wild type strain was able to achieve weight loss of up to 86% for polyester PU foam after 14 days, while the mutated strain achieved this after just four days. This, the team said, means they are the most efficient PU foam-degrading strains identified thus far.
They also identified a novel cutinase gene, purh, that encodes for the cutinase enzyme they found was substantially responsible for the PU degradation. This was cloned, and recombinant PurH was expressed in E. coli. It was found to efficiently degrade PU foam into a powder.
The team suggest that the new and highly efficient PU foam-degrading strain, and the enzyme it produces, could be a leap forward for the biological depolymerisation and recycling of PU foam.
The work has been published in the Journal of Hazardous Materials.
