Plastic waste up-cycling potential of Streptomyces spp.: a genomic examination

The accumulation of plastic waste has become an ever-growing global problem, with world production of plastic materials reaching >380 million tons annually and only predicted to increase in the coming years. An efficient means of disposing and recycling plastic waste is urgently needed. Due to environmental risk factors and high energy consumption of mechanical and chemical recycling methods research focus has shifted towards biological means of recycling. Biocatalysis offers an environmentally friendly and potentially very efficient strategy for plastic waste degradation and valorization by utilizing the reaction products in downstream biosynthetic reactions (up-cycling) (1). Streptomyces spp. are highly regarded as bioactive secondary metabolite producers, however, the genus proved a promising source of industrially relevant enzymes as well (2). Leveraging this unique combination of biosynthetic and biocatalytic capabilities a collection of Streptomyces strains was screened for their plastic-degrading potential using different polyester-based polymers. Strains that could degrade and utilize plastic polymers and monomers as the sole carbon source were sequenced and the genomes searched for homologs of known plastic-degrading enzymes and biosynthetic clusters for bioactive compounds. Enzymes capable of degrading both conventional petrochemical and bioplastics were detected in the genomes of all tested strains. Interestingly, enzymes closely related to highly active poly(ethylene terephthalate) degrading enzymes were found in most strains. As expected, analysis of the biosynthetic potential yielded numerous gene clusters associated with polyketide, non-ribosomal peptide and lassopeptide synthesis. Finally, the ability to convert plastics to biologically active metabolites was confirmed using Streptomyces sp. PM1. When grown on polyurethanes as the sole carbon source this strain showed antimicrobial activity against Staphylococcus aureus. In conclusion, this work high