Rapid Biodegradation of Low-Density Polyethylene (LDPE) Without Pre-Treatment by Bacillus Strains Isolated from Garbage Dumpsites

The recalcitrant Low-Density Polyethylene (LDPE) is a multifaceted polymer. Therefore, it has slowly gained popularity for ease of access while simultaneously becoming a threat to nature. Investigation of diverse bacteria and exploring their natural ability to degrade LDPE has become a pressing matter in countries like Bangladesh, where thoughtless utilization and indiscriminate disposal of plastics are practiced. This study examined the potential of bacteria to degrade the untreated low-density polyethylene (LDPE). Bacteria were isolated from partially degraded plastic wastes collected from three open garbage dump sites in Dhaka, Bangladesh. Incubation of untreated plastic film inoculated with isolated bacteria resulted in significant weight loss (16%-26%). Both the SEM and Optical Microscope images at 2000x, and 1000x magnifications respectively, revealed surface topology modifications in forms of erosion, cracks, grooves, and minor holes. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the transformation of recalcitrant LDPE film.16S rRNA gene sequencing identified the potential bacteria as Bacillus pumilus strain FMA1, Bacillus aerius strain FMA2, Bacillus sp. (in: firmicutes) strain FMA3, Bacillus cereus strain FMA4, and Bacillus atrophaeus strain FMA5. A significant finding was the detection of Bacillus aerius strain FMA2 and Bacillus atrophaeus strain FMA5, which have no previous LDPE degradation records. More importantly the Bacillus aerius strain FMA2 showed the best degradation potential among the five isolates. A Phylogenetic Tree constructed using the DNA sequence data signified the evolutionary relationship among the bacterial species. This research reveals the prevalence of Bacillus species as soil bacterium in Dhaka city along with their inherent biodegradation capabilities, emphasizing an eco-friendly management of emerging plastic pollution.