Identification and Molecular Characterization of Polyethylene Degrading Bacteria from Garbage Dump Sites in Adama, Ethiopia

Abstract

Degradation of polyethylene is a great challenge due to its ever-increasing production and resulting pollution. This study was focused on identifying and characterizing polyethylene degrading bacterial isolates. Microorganisms were isolated from waste disposal site in Adama, Ethiopia. Carbon free basal medium supplemented with polyethylene was used to screen the bacterial isolates for biodegradation potential. The pure bacterial isolates were characterized by Gram’s staining, biochemical tests, and MALDI-TOF MS analysis. The detection of alk B gene was carried out using PCR and 16s rRNA sequencing was employed for identification of an isolate that wasn’t identified by MALDI-TOF MS. Sequencing revealed the bacterium as Bacillus sp. with a 91% similarity with Rossellomorea oryzaecorticis and a phylogenetic assessment was carried out using MEGA 11. The bacterial isolates were screened for enzymes such as: esterase, protease, and pectinase and the optimum pH, temperature and polyethylene concentration were determined for the isolates. The isolates were then subjected to biodegradation assay with untreated and UV treated polyethylene films in mineral salt medium for 1 month. The highest results based on weight loss % of untreated polyethylene were 4.25% and 1.93% Pseudomonas Sp.; 1.96%, 1.14%, and 1.53% Bacillus sp. with UV treatment the weight loss % was 17.96% and 19.9% Pseudomonas sp., 13.75%, 8.63%, and 4.79% Bacillus sp., and 6.77% Acinetobacter sp. Scanning Electron Microscopy used to observe changes in surface showed cracks on the polyethylene material after incubation with bacterial isolates. Pseudomonas and Bacillus sp. were found to have great capacity in polyethylene degradation and can therefore be used to facilitate an eco-friendly removal of plastic waste from the environment and further studies can be carried out to improve their enzymatic activity and thereby increasing degradative ability of the newly found isolates.