Potential for Polyethylene Terephthalate (PET) Degradation Revealed by Metabarcoding and Bacterial Isolates from Soil Around a Bitumen Source in Southwestern Iran

The rapid global growth of plastic production and waste are harbingers of increasing pollution in terrestrial and marine ecosystems for which safe and effective methods of disposal and degradation must be pursued. In the present study, metabarcoding and culture-based studies have been carried out to provide insights into polyethylene terephthalate (PET) biodegradation potential. Post-consumer PET films and powder were exposed to soil samples obtained from an aged oil bitumen spring site in Southwest Iran. To investigate microbial community composition, metagenome was extracted and hypervariable V3-V4 were sequenced (metabarcoding). Comparison of 16S amplicon metagenomic profiles between samples shows that Bacillus spp. and Halomonas spp. were the most abundant among bacterial genera present in soil samples from the vicinity of the oil seep, while Sphingomonas genus was most frequent in sample C collected from a region ~ 0.5 km distant of the oil seep. In the culture-based approach, Brevibacillus and Pseudomonas spp were isolated and analyzed for PET degradation. Field Emission Scanning Electron Microscope (FE-SEM) analysis shows two isolates had been colonized on PET film surface forming biofilm-like structures. PET degradation components were investigated by Gas Chromatography- Mass Spectrometry (GC-MS) which revealed the presence of aliphatic and aromatic compounds in the bacterial media. In addition, X-Ray diffraction (XRD) analysis showed reduction in crystallinity region peaks after 90 days of incubation with bacteria at 32°C. The diversity of the microbial community and the presence of PET degrading bacteria indicate a potential of the native oil seep-contaminated ecosystem for plastic degradation which is acquired following long-term adaptation to petroleum compounds.