Discovery of a polyester polyurethane-degrading bacterium from a coastal mudflat and identification of its degrading enzyme

Biodegradation of polyurethane (PU) plastics is a lower cost and more environmentally friendly approach to the regeneration of waste plastics than the landfill or incineration alternatives. Currently, however, the lack of efficient degradation strains and their enzymes is restricting the development of viable large-scale waste PU regeneration. In this study, a wild strain (LTX1) is isolated from a coastal mudflat, and then a mutant strain (MLTX1) with higher degradation efficiency is obtained by UV mutagenesis. Both the LTX1 and MLTX1 strains are able to achieve a more than 80 % weight loss of PU foam after 12 days treatment, making them the most efficient PU foam-degrading strains available to date. The PU foam degradation is characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). A novel gene, purh, encoding one of the cutinases is cloned using genomics and transcriptomics, and its recombinant PurH, capable of efficiently degrading PU foam, is expressed in Escherichia coli and identified. The discovery of this highly-efficient PU foam-degrading strain and its enzyme may represent a leap forward in the biological depolymerization and recycling of PU foam.