Biodegradation of low-density polyethylene by novel halophilic bacteria from mangrove ecosystem

Abstract

Low-density polyethylene (LDPE) is identified as the primary constituent (approximately 18.9%) in plastic waste pollution. Crystalline structure, high molecular weight, and hydrophobic nature make LDPE recalcitrant to degradation. In the current study, the biodegradation of LDPE was studied by using three novel Malaysian mangrove bacterial isolates Brevundimonas naejangsanensis (strain MGS1), Arthrobacter crystallopoietes (strain SW4), and Arthrobacter pokkalii (strain PD2). Biodegradation of UV-treated LDPE was determined by the gradual increase in microbial count and production of laccase and lipase enzymes over a period of thirty days. All the isolates reduced the weight of the residual polymer and modified the chemical structure of LDPE by forming carbonyl and hydroxyl groups as a result of oxidation reactions by enzymes. Strain MGS1 reduced the maximum weight by 4.64 ± 0.5% and produced maximum laccase (2.19 ± 0.15 U/mL) and lipase enzyme (1.35 ± 0.05 U/mL). Field emission scanning electron microscopy (FESEM) showed visual images of bacterial colonization, and surface erosion (cracks/holes) on the LDPE surface. The production of enzymes reduced the hydrophobicity of the LDPE as evidenced by the biofilm formation, addition of new functional groups, surface erosion, and weight loss. The study is significant in addressing the biodegradation of plastic waste in Malaysia by exploring the mangrove microbiome.