Degradation of agricultural polyethylene film by greater wax moth (Galleria mellonella) larvae and screening of involved gut bacteria

Abstract

Agricultural polyethylene (PE) mulch films persist in ecosystems, demanding efficient biodegradation. Previous studies have demonstrated the ability of greater wax moth (Galleria mellonella) larvae to feed on plastic bags and foams. However, limited characterization of efficient PE-degrading strains from their gut microbiota, combined with insufficient mechanistic insights into host-microbe synergy, has hindered progress. This study demonstrates that Galleria mellonella larvae can effectively degrade PE mulch films through physical chewing, microbial action, and gut metabolism. Feeding by Galleria mellonella resulted in a 35 % weight loss of PE mulch films within 30 days; FT-IR, TGA, and GPC analyses confirmed chemical depolymerization of PE. Antibiotic suppression of gut microbiota reduced PE consumption by 37 %, validating microbial indispensability. Three novel strains-Pseudomonas putida ZSA123, Enterobacter hormaechei LBA140, and Lysinibacillus fusiformis LBB122-were isolated, constituting the first documented evidence of these bacterial species functioning as highly efficient plastic-degrading symbionts in wax moths, with Pseudomonas putida and Lysinibacillus fusiformis representing particularly novel discoveries in plastic-consuming insects. These strains achieved 5.68-9.76 % PE weight loss in vitro with evident surface erosion and significant mechanical deterioration, indicating effective polymer chain scission. Metabolomics detected diet-specific hydroxylated fatty acid derivatives from PE chain oxidation alongside up-regulated β-oxidation carriers, suggesting host assimilation of oxidized PE fragments. Crucially, bran co-diet resolved mortality issues while maintaining 26.0 % degradation efficiency, offering a scalable dual-track strategy that couples plastic waste treatment with insect biomass production. This work provides fundamental insights into insect-microbe synergistic mechanisms in PE degradation and paves the way for sustainable management of agricultural plastic waste.

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