Recent studies have indicated that Galleria mellonella larvae ingest polyethylene films and the degradation mechanism could inspire biotechnological exploitation for degrading plastic to eliminate global pollution from plastic waste. In this study, we tested the chemical compositions of masticated and ingested different plastic types by G. mellonella. High throughput sequencing of 16S rRNA gene was used to characterize the alteration of the microbial communities derived from salivary glands, gut contents and whole G. mellonella larvae. Our results indicated that G. mellonella is able to masticate polyethylene (PE), expanded polystyrene (EPS) and polypropylene (PP) and convert it to small particles with very large and chemically modified surfaces. The characteristics of the polymer affect the rate of damage. Formation of functional carbonyl groups on the appearance of oxidized metabolic intermediates of polyolefins in the frass samples observed. We found that the mastication of EPS, PP or PE could significantly alter the microbial composition in the gut content while it did not appear to influence the salivary glands microbial community. Representatives of Desulfovibrio vulgaris and Enterobacter grew with the PE diet while mastication of polystyrene and polypropylene increased the abundance of Enterococcus. The evaluation of bacterial communities in whole larvae confirmed the obtained result and additionally showed that the abundance of Paenibacillus, Corynebacterium and Commamonadaceae increased by Styrofoam (EPS) consumption.

Low-density polyethylene (LDPE), biaxially oriented polypropylene (BOPP), and expanded polystyrene (EXPS) are the most common plastics found in every home of the world, but only ~ 10% enter the recycling chains. Consequently, the study of plastic biodegradation by microorganisms and insects, such as the wax moths, has gained special interest. Galleria mellonella (L.) has been shown to consume single-layered polyethylene and polystyrene, though biological impacts of this consumption have been rarely reported. We evaluated the consumption of different plastics by G. mellonella larvae (L7, mean size: 25–30 mm) and its effect on larval duration, survival, and development. For this, we offered the larvae five diets: single-layered LDPE, EXPS, BOPP, triple-layered polyethylene (SB, for silo-bags), and a control with beeswax. We recorded the state and weight of the materials and the state of larvae until they reached the adult stage. Larvae consumed more PE (both LDPE and SB) and EXPS than BOPP; still, they were able to emerge as adults in all treatments. Larvae that consumed plastics turned into pupal stage faster than those that consumed beeswax, regardless of the type and amount of plastic consumed. This is the first report of wild G. mellonella larvae in Argentina consuming biaxially polypropylene and silo-bags.

Nanomaterials of different sizes and diameters are frequently used in various industrial areas, due to the rapid development of nanotechnology. Hence, it leads to toxic effects on the environment and non-target organisms, and adverse effects such as oxidative stress and membrane damage in cells and tissues are occurred. Some biomarkers such as the accumulation of intermediate products, detoxification of the immune system, or xenobiotic are used in the detection of toxic effects of exogenous substances in living organisms. In this study, the effects on catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione-s-transferase (GST) enzyme activities to determine the toxic effects of TiO₂ NPs on antioxidant defense system, acetylcholinesterase (AChE) activity to determine their neurotoxic effects, and total hemocyte count (THC) to determine their effect on the immune system were investigated in model organism Galleria mellonella larvae. It was determined that major amounts of Ti were mostly eliminated through the Malpighian tubules. Moreover, TiO₂ NPs in different concentrations caused the formation of reactive oxygen species in G. mellonella and lead to an increase in antioxidant enzymes. Decreases were found in THC due to the TiO₂ NP application. As a result, it was concluded that TiO₂ NPs caused accumulation in tissues of the model organism G. mellonella, resulting in oxidative stress and has adverse effects on the immune system.