Characterization of low-density polyethylene (LDPE) films degraded using bacteria strains isolated from oil-contaminated soil

Abstract

This study assessed the low-density polyethylene (LDPE) film degradation potential of microorganisms isolated from oil-contaminated soil and also analyzed the morphological and chemical composition of LDPE films after the biodegradation period. The bacteria strains isolated from oil-contaminated soil were standardized and used to degrade the pretreated LDPE films in mineral salt media. Thereafter, they were incubated for 78 days at 37°C in an incubator shaker, and the degraded LDPE films were analyzed quantitatively and qualitatively (using scanning electron microscope (SEM) images and energy dispersal x-ray (EDX)). Isolates A32 and BTT4 amongst other bacteria isolates showed the highest LDPE film degradation activity, with a weight reduction of 71.80% and 89.72% respectively, and were identified using the 16S rRNA sequencing technique. The EDX results showed that LDPE film incubated with A32 has the highest reduction in carbon and nitrogen (23.8% and 44.9% respectively) when compared with the Control. However, LDPE film incubated with BTT4 had an increase in calcium and chlorine (139% and 40% respectively), when compared with the control. Similarly, the SEM images showed the appearance of pinholes, cracks and particles on the surfaces of LDPE films incubated with A32 and BTT4 contrary to the controls. A32 and BTT4 were identified as Proteus mirabilis (Accession number: MN124173.1) and Proteus mirabilis (Accession number: KY027145.1) respectively. Proteus mirabilis showed viable plastic biodegradation potentials and may be useful in the management of plastic waste, leading to a reduction in global plastic waste and a clean environment.

Keywords: Biodegradation; environment; microorganism; plastic waste; scanning electron microscope.