Biodegradation of Low-Density Polyethylene Film by UV Irradiated and Non-Irradiated Pseudomonas Aeruginosa D5

Abstract

Low-density polyethylene (LDPE) constitutes 60% of total plastic production, and non-degradable polyethylene carry bags are the most common type of solid waste found. Their recalcitrance in the environment is thus a major concern for environmentalists. This study investigated the potential of Ultraviolet (UV) induced mutation in enhancing biodegradation of LDPE films by two diesel degrading bacteria, Alcaligenes faecalis D4 and Pseudomonas aeruginosa D5. The two strains were screened for LDPE utilisation, and the best strain was subjected to UV irradiation. The successful mutant was then used for LDPE biodegradation studies in vitro for 28 days and compared with the wild-type strain. The rate of LDPE film utilisation was estimated using cell density measurement, weight loss and FTIR spectroscopy. Only P. aeruginosa D5 was able to survive UV irradiation at different exposure times. The mutant strain was able to utilise LDPE, resulting in cell density across the incubation time and corresponding weight loss of the films after 28 days, resulting in a 9% better weight reduction than the wild type strain after incubation. The mutant strains also demonstrated significant chemical alterations, including the introduction of carboxylic acids, amines, and alkenes. The detection of multiple carbonyl peaks (2399.05 cm-1, 1100.56 cm-1) in untreated LDPE and their shifts in mutant-treated samples (2498.63 cm-1, 1700.65 cm-1) indicate oxidative degradation, leading to the formation of aldehydes, ketones, and carboxylic acids. These findings reveal the LDPE utilisation potentials of mutant P. aeruginosa as well as the application of mutation to enhance pollutant bioremediation.