Identification and molecular characterization of Polyethylene degrading bacteria from garbage dump sites in Adama, Ethiopia

Degradation of Polyethylene is a great challenge due to its resistance to biodegradation. This study was aimed at identifying and characterizing Polyethylene degrading bacterial isolates (PDIs). Microorganisms were isolated from a waste disposal site in Adama, Ethiopia. A carbon-free basal medium supplemented with Polyethylene was used to screen PDIs. The pure bacterial isolates were characterized by Gram staining, biochemical tests, and MALDI-TOF MS analysis. PCR amplification for the alkB gene was carried out. Both 16 s rRNA sequencing and MALDI-TOF MS were done for bacterial identification. Bacillus, Pseudomonas, and Acinetobacter species were identified. Certain enzyme activities were obtained for PDIs. Considerable weight reductions for Polyethylene were detected after these isolates had been treated with UV for one month. The highest weight loss was detected for P. balearica PDI-17 (4.25%), and the lowest weight reduction was detected against B. subtilis PDI-27 (1.14%) without any treatment of Polyethylene. However, after the treatment of Polyethylene with UV treatment, the minimum and maximum weight re-ductions were recorded for B. subtilis PDI-27 (4.788%) and P. balearica PDI-17 (19.9%). The optimum pH, temperature and Polyethylene concentration were obtained for certain PDIs. SEM was used to observe changes in the surface with cracks on the polyethylene material after incubation with bacterial isolates. Pseudomonas and Bacillus sp. were found to have an excellent capacity for polyethylene degradation. Therefore, they can be used to facilitate the eco-friendly removal of plastic waste from the environment. Further studies can be carried out to improve their enzymatic activity, thereby increasing the degradative ability of the newly found isolates.