Biological degradation of macroplastics and microplastics by greater wax moth larvae (Galleria mellonella): evidence, gut microbiome, and proposed mechanisms

Plastic pollution, encompassing macroplastics and microplastics, is an increasing global environmental problem that remains difficult to address using conventional methods. Larvae of the greater wax moth, Galleria mellonella, have attracted attention as a biological model for investigating plastic consumption and transformation. This review synthesizes evidence concerning their interactions with polyethylene, polystyrene, polypropylene, polyvinyl chloride, bioplastics, and complex plastic waste. The reviewed studies used heterogeneous substrates, including macroplastic films, sheets, foams, and fragments, as well as powders and microplastic particles. These categories require distinction because particle size and geometry influence surface-area-to-volume ratio, larval mastication and ingestion, microbial colonization, analytical recovery, and apparent degradation kinetics. Evidence obtained from macroplastic substrates therefore cannot be directly extrapolated to microplastic degradation. Reported consumption and transformation efficiencies varied according to polymer type, substrate form and dimensions, exposure duration, feeding regime, larval density, pretreatment, and analytical method. Gut-associated taxa, including Bacillus, Pseudomonas, Enterococcus, and Enterobacter, were recurrently reported; however, their detection or enrichment indicates association with plastic exposure rather than definitive evidence of direct degradation. Chemical, metabolomic, microbiome, and proteomic findings support proposed oxidative and downstream metabolic pathways, although complete depolymerization, bioassimilation, and mineralization remain insufficiently demonstrated across polymers and size classes. Despite inconsistent experimental designs and variable substrate characterization, G. mellonella remains valuable for identifying candidate enzymes, microorganisms, and host-microbiome interactions. Future studies should use chemically characterized substrates with defined size classes, appropriate controls, molecular-weight analysis, and isotope tracing to distinguish fragmentation from chemical transformation, bioassimilation, and mineralization.