Isolation of the Gut Microbiome of Galleria mellonella Sp. (Lepidoptera: Pyralidae) Larvae and Its Role in the Digestion of Polyethylene Plastic

Plastic is one of the most consumed polyethylene-containing materials in human society, and the release of plastics into nature or their incineration is considered the most critical environmental problem. The scope of this study is extraction gut bacteria from Galleria mellonella larvae that digest plastic. Galleria mellonella larvae were collected from beehives in Gonabad City, Razavi Khorasan Province (Iran), in June 2022. Three diets of wax comb-polyethylene, polyethylene, and wax comb-were used to study the feeding rate of the larvae. All cultured bacteria were inoculated separately to the carbon-free basal agar medium (CFBAM) culture medium, and a polyethylene film (30 x 30 mm) was put on the bacteria and incubated for 40 days. Visualization of the plastics by optical atomic force (AFM) and scanning electron microscopy (SEM) also illustrated biodegradation. A total of 5 bacterial and 1 fungal species (Aspergillus flavus) were extracted from larvae fed with three diets. These bacteria consisted of Enterococcus sp., Acinetobacter sp., Bacillus sp., Enterobacter sp., and Staphylococcus sp. Bacillus sp. in most diets. In CFBAM, Enterobacter could grow on pure polyethylene film and survive for 40 days. Regarding plastic brand types fed by larvae, garbage bags lost 80% of their weight, compared with 75% of the weight in freezer bags and 60% in shopping bags, considering the reduction of plastic mass degraded by G. mellonella larvae and the ability of Enterobacter sp. to digest under the digestion condition.

Automated summary

This study aimed to extract gut bacteria from Galleria mellonella larvae that can digest plastic. The results showed that G. mellonella larvae can biodegrade polyethylene plastic and various bacterial and fungal species were isolated. The type of bacteria and feed affected the rate of plastic degradation.