A survey of intact low-density polyethylene film biodegradation by terrestrial Actinobacterial species

Low-density polyethylene (LDPE) polymer is mainly used in the production of plastic bags and food packaging making up the largest volume of plastic pollutions. These polymers are potential substrates for bacteria in the bioremediation process. In this study, soil samples were collected from different plastic landfills in Iran and subsequently enriched in specific media (polyethylene as carbon source) to increase the population of LDPE-degrading bacteria. Seventeen PE-degrading bacteria, some novel, were isolated from Iranian soil samples and identified using 16S rDNA gene sequencing. These isolates were capable of degrading PE in a limited incubation period without the need for physicochemical pretreatments and comprise mostly of Actinobacteria which include the three genera ofStreptomyces,Nocardia, andRhodococcus. The isolates belonged to 17 different species of gram-positive Actinobacteria. In all, 11 species of the genusStreptomyces, 3 species of the genusRhodococcus, and 3 species of the genusNocardiawere identified. The isolates with less than 99% 16S rRNA gene similarity to previously known species were suspected to be new species. Various analyses (weight loss, SEM, FTIR, and tensile strength test) to determine polyethylene biodegradation rate were carried out after a 60-day incubation period. Analysis of polyethylene biodegradation elucidates that Actinobacteria have a high ability for biodegradation of polyethylene-based plastics.Streptomycessp.IR-SGS-T10showed the highest reduction in weight of the LDPE film (1.58 mg/g/day) after 60 days of incubation without any pretreatments.Rhodococcussp. IR-SGS-T11 shows the best reduction in the tensile property of LDPE film, while results from FTIR study forStreptomycessp. IR-SGS-Y1 indicated a significant change in structural analysis.

Automated summary

This study isolated 17 PE-degrading bacteria from soil samples in Iranian plastic landfills, belonging to 17 different species of gram-positive Actinobacteria. These bacteria demonstrated high biodegradation ability for polyethylene-based plastics after a 60-day incubation period, with Streptomyces sp. IR-SGS-T10 showing the highest degradation rate, Rhodococcus sp. IR-SGS-T11 exhibiting the best reduction in tensile properties, and Streptomyces sp. IR-SGS-Y1 showing significant structural changes in FTIR analysis.