Native Polyethylene Biodegradation by Gut-Associated Bacteria from Galleria mellonella Larvae: Multi-Method Evidence Without Abiotic Pretreatment

The accumulation of polyethylene (PE) in the environment represents a persistent ecological challenge, and the search for biological agents capable of degrading it without relying on prior abiotic pretreatment remains an active area of research. In this study, three bacterial strains—Pseudomonas aeruginosa, Enterobacter hormaechei, and Acinetobacter pittii—were isolated from the gut of Galleria mellonella larvae dietarily induced with native low-density polyethylene (LDPE), without prior UV, thermal, or chemical treatment. Molecular identification was confirmed by 16S rRNA gene sequencing and maximum-likelihood phylogenetic analysis. Degradative activity was assessed using a multi-method approach: a colorimetric DCPIP assay, gravimetric mass loss at 45 days, FTIR-ATR spectroscopy, SDS-PAGE, and scanning electron microscopy. All three strains showed metabolic activity toward LDPE, with A. pittii producing the greatest mass loss. FTIR analysis revealed the appearance of hydroxyl and C–O-containing functionalities without detectable carbonyl accumulation, a pattern consistent with the hypothesized activation of an oxidative pathway mediated by the alkane hydroxylase (AlkB) system, pending direct molecular/biochemical confirmation. These results expand the still-limited number of reports on native-PE-degrading activity documented individually for E. hormaechei and A. pittii and reinforce the value of the G. mellonella gut microbiome as a reservoir of bacteria with biotechnological potential for plastic waste management.