Marine Streptomyces spp. isolates with synthetic polyesters-degrading activity

The rapid expansion of global plastic production in the last number of decades (>355 million tonnes in 2017), coupled with poor waste management, has resulted in an estimated 5–12 million metric tonnes of plastic waste entering our oceans. Packaging applications account for much of the current waste production, and commonly include polyethylene- and polyethylene terephthalate (PET)-based materials that are resistant to natural degradation processes, particularly in marine environments. In response to this global marine pollution issue and the continuing demand for effective treatment of such plastics in terrestrial environments (e.g. 27.1 million tons of annual, post-consumer plastic waste in Europe alone), researchers have focused on addressing the biodegradation of recalcitrant plastic waste such as PET. To this end, we screened 20 Streptomyces spp. strains isolated from marine sponges for polycaprolactone (PCL)-degrading activity, which is considered a model substrate for PET. Although the Streptomyces genus is commonly explored for natural products discovery, little is still known about its potential for polymer degradation. Genomic analysis of two of the Streptomyces isolates which screened positive for PCL-degrading activity were found to have PET-hydrolase gene homologs that shared 41 % identity to the well-characterised PETase from Ideonella sakaiensis 201 F6. One of these genes was subsequently heterologous expressed in E. coli in order to further characterise the enzymatic activity and other biochemical properties of the enzyme.