Streptomyces coeruleorubidus strain SALG1 derived seashore plastic bottle for the biodegradation of untreated plastic polymers

Plastic pollution has become a significant environmental concern due to the widespread use and persistence of polyethylene (PE) in various industries. In this study, soil samples containing plastic waste were collected from a public landfill site, along with plastic bottles gathered from the shore of Sidi Ali Lebher in the Bejaia region, Algeria. In total, nine strains of PE-degrading actinobacteria were isolated using PE as sole carbon source. The SALG1 strain was isolated from plastic bottles and selected for its high enzymatic potential and effectiveness in degrading PE. Selected from nine actinobacteria isolates, it was identified as Streptomyces coeruleorubidus with 98.28% similarity to Streptomyces coeruleorubidus type strain ISP 5145 T based on the 16S rRNA gene sequence analysis. The growth of SALG1 was evaluated using polyethylene glycol (PEG) as the sole carbon source, demonstrating a significant reduction in PEG concentration over a 14-day period, accompanied by biomass accumulation. Furthermore, SALG1 exhibited biosurfactant production and hydrophobicity, indicating its potential to interact with hydrophobic substrates like PE. Biodegradation experiments conducted over 2 and 6 months revealed SALG1’s capability to degrade colorless and black PE (9.18% and 5.22%), as well as polystyrene (PS) and polyethylene terephthalate (PET) (0.25% and 0.42%) in both liquid and solid media. Moreover, the presence of Tween 80 enhanced degradation percentages, particularly in liquid media, suggesting its utility as a potential biostimulant. Structural changes induced by SALG1 activity in polymer films were characterized using X-ray diffraction (XRD) and infrared spectrophotometry (ATR), as well as the thermogravimetric analysis (TG/DTG) providing valuable insights into the degradation mechanism.