Biodegradation of low-density polyethylene by actinomycete Nocardia asteroides isolated from agricultural soils

Plastic residues from agricultural mulches, particularly low-density polyethylene (LDPE), cause severe soil pollution. In this study, an actinomycete strain, Nocardia asteroides PE3.3, isolated from agricultural soil, degraded LDPE films and powders with a weight loss of 1.5 ± 0.1 % and 11.0 ± 0.4 % after 30 d, respectively. Degradation was accompanied by increased surface roughness, carbonyl formation, and oxidation of the polymer chains. The products were identified as long-chain alkanes, alcohols, ketones, and carboxylic acids. Proteomic analysis revealed that extracellular peroxidases catalyze the oxidative cleavage of LDPE, while intracellular monooxygenase, alcohol dehydrogenase, and aldehyde dehydrogenase further metabolize the degradation intermediates via β-oxidation. It has been further confirmed that LDPE can be oxidized degraded by two peroxidases secreted by PE3.3. This study provides first proteomic-level elucidation of LDPE biodegradation in N. asteroides, establishing a verified enzymatic pathway that supports its application in microbial plastic remediation.