Biodegradation of sachet water polyethylene plastic waste using bacteria isolates

Introduced in the early 1990s, Nigeria's most consumed potable water packaging material is dumped indiscriminately into various environments despite concerns about its harmful effects on these environments. The study was designed to isolate and characterise potential microbial degraders and their degradation potentials using various methods. Various environmental samples (soil, sediment, and marine water) were obtained using standard protocols. Microplastic from the sachet water (SW) plastic was generated mechanically using a sterile grater and used to enrich the various samples from which potential degraders were obtained. The isolates were further screened for their ability to degrade crude oil. Positive hydrocarbonoclastic isolates were used for the biodegradation experiments of the polyethylene sheets (3 × 3 cm) via weight loss, fourier transform infrared spectroscopy (FT-IR), and gas chromatography (GC-MS). A total of 38 experiments plus one control were set up. After incubation, a total of ten (10) very turbid flasks and their control were selected for FT-IR spectroscopy. Following FT-IR, the best (n = 1) experiment and its control were subjected to GC-MS. Selected isolates were confirmed using molecular characterisation to be Pseudomonas aeruginosa (PMB₄₅) and Rossellomorea aquimaris (HBSD₂₈). Plasmid profiling for the alkB gene was positive for isolate PMB₄₅ and negative for HBSD₂₈. Weight loss gave a biodegradation rate of 22.5% for SW sheets, respectively. Furthermore, FT-IR positive sheets had functional groups such as ketones, carbonyl, carboxylic, and amino groups, and this was consistent with the GC-MS report that showed a reduction in carbon atoms, signifying degradation in the broths containing the positive isolate. Our findings indicate that, R. aquimaris (HBSD₂₈) and P. aeruginosa (PMB₄₅) have potential to degrade SW plastic waste. Further studies aimed at optimising isolates, and revealing pathways and enzymes elaborated in polyethylene biodegradation should be prioritised.