Plastics are synthetic polymers derived from fossil oil and largely resistant to biodegradation. Polyethylene (PE) and polypropylene (PP) represent ∼92% of total plastic production. PE is largely utilized in packaging, representing ∼40% of total demand for plastic products ( www.plasticseurope.org ) with over a trillion plastic bags used every year []. Plastic production has increased exponentially in the past 50 years ( Figure S1 A in Supplemental Information , published with this article online). In the 27 EU countries plus Norway and Switzerland up to 38% of plastic is discarded in landfills, with the rest utilized for recycling (26%) and energy recovery (36%) via combustion ( www.plasticseurope.org ), carrying a heavy environmental impact. Therefore, new solutions for plastic degradation are urgently needed. We report the fast bio-degradation of PE by larvae of the wax moth Galleria mellonella, producing ethylene glycol.

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2 Yamada-Onodera K.

Mukumoto H.

Katsuyaya Y.

Saiganji A.

Tani Y. Degradation of polyethylene by a fungus. Penicillium simplicissimum YK. 3 Bonhomme S.

Cuer A.

Delort A.-M.

Lemaire J.

Sancelme M.

Scott C. Environmental biodegradation of polyethylene. -1, a signature for ethylene glycol, confirming PE degradation. More recently, Yang et al. reported bacterial degradation of PE over several weeks [ 4 Yang J.

Yang Y.

Wu W.-M.

Zhao J.

Jiang L. Evidence of polyethylene biodegradation by bacterial Strains from the guts of plastic-eating waxworms. -2 day-1) of another plastic, poly(ethylene terephthalate) (PET) by a microbial consortium including a newly isolated bacterium, Ideonella sakaiensis, was described recently [ 5 Yoshida S.

Hiraga K.

Takehana T.

Taniguchi I.

Yamaji H.

Maeda Y.

Toyohara K.

Miyamoto K.

Kimura Y.

Oda K. A bacterium that degrades and assimilates poly(ethylene terephthalate). PE comprises a linear backbone of carbon atoms ( Figure S1 B), which is resistant to degradation. Although PE is believed not to be susceptible to bio-degradation, a few attempts have been made, as PE is the most common packaging plastic. Slow (weeks/months) PE biodegradation has been observed, given appropriate conditions. For example, modest degradation of PE was observed after nitric acid treatment and incubation for 3 months in a liquid culture of the fungus Penicillium simplicissimum []. Slow PE degradation was also recorded after 4 to 7 months exposure to the bacterium Nocardia asteroides []. In both cases, fourier transform infrared spectroscopy (FTIR) analysis of treated samples revealed formation of an absorbance peak around 3,300 cm, a signature for ethylene glycol, confirming PE degradation. More recently, Yang et al. reported bacterial degradation of PE over several weeks []. However, no production of ethylene glycol from the biodegradation was described. The authors reported that PE biodegradation depended on the activity of microorganisms present in the gut of the larvae of the Indian mealmoth Plodia interpunctella (two bacterial strains, Bacillus sp. YP1 and Enterobacter asburiae YT1). Faster biodegradation (∼0.13 mg cmday) of another plastic, poly(ethylene terephthalate) (PET) by a microbial consortium including a newly isolated bacterium, Ideonella sakaiensis, was described recently []. Although PET is a resistant material, one might expect its biodegradation to be easier than PE, as PET has a polyester backbone and can be hydrolysed. We report here the fast biodegradation of PE by the wax worm, the caterpillar larva of the wax moth Galleria mellonella of the snout moth (Pyralidae) family of Lepidoptera.

-2 h-1, which is markedly higher than the rate of PET biodegradation by a microbial consortium recently reported [ 5 Yoshida S.

Hiraga K.

Takehana T.

Taniguchi I.

Yamaji H.

Maeda Y.

Toyohara K.

Miyamoto K.

Kimura Y.

Oda K. A bacterium that degrades and assimilates poly(ethylene terephthalate). Figure 1 Polyethylene degradation by Galleria mellonella. Show full caption (A) Plastic bag after exposure to ∼100 wax worms for 12 hours. (B) Magnification of the area indicated in A. (C) Gravimetric analysis of homogenate-treated versus untreated polyethylene (PE), showing a reduction (13%) of mass per unit of area in the former. (D,E) FTIR analysis of the homogenate-treated and control PE films. (F,G) Atomic Force Microscopy on homogenate-treated (G) and untreated (F) PE film (representative examples of 3 topographic maps each). When a PE film was left in direct contact with wax worms, holes started to appear after 40 minutes, with an estimated 2.2±1.2 holes per worm per hour ( Table S1 A). Figure 1 A,B shows the result of leaving ∼100 wax worms in contact with a commercial PE shopping bag for ∼12 hours, which caused a mass loss of 92 mg. To exclude the possibility that mechanical action of the masticatory system was solely responsible for the observed PE breakdown, worm homogenate was smeared on and left in contact with PE films. Gravimetric analysis of the treated samples confirmed a significant mass loss of 13% PE over 14 hours of treatment (one-way ANOVA, p = 0.029) compared to the untreated samples ( Figure S1 C and Table S1 B,C). This corresponds to an average degradation rate of 0.23 mg cm, which is markedly higher than the rate of PET biodegradation by a microbial consortium recently reported [].

-1 being the classical signatures of PE (-1 was seen ( 4 Yang J.

Yang Y.

Wu W.-M.

Zhao J.

Jiang L. Evidence of polyethylene biodegradation by bacterial Strains from the guts of plastic-eating waxworms. 3 Bonhomme S.

Cuer A.

Delort A.-M.

Lemaire J.

Sancelme M.

Scott C. Environmental biodegradation of polyethylene. 6 Zuchowska D.

Hlavata D.

Steller R.

Adamiah W.

Meissner W. Physical structure of polyolefin-starch after ageing. -1 appeared in the treated sample, which is the classical signature of the carbonyl bond ( To test if the PE polymer was chemically degraded by contact with the worm homogenate, we carried out FTIR analysis. When the FTIR probe was pointed on untreated samples, the spectroscopic results confirmed the identity of the PE film, with peaks at 2,921 and 2,852 cmbeing the classical signatures of PE ( Figure 1 D, black line). However, when the probe was pointed on sample smeared with worm homogenate, an additional peak at ∼3,350 cmwas seen ( Figure 1 D, red line). This FTIR peak corresponds to the one previously described as the ethylene glycol signature (also compare Figure 1 E with Figure 4B in []) []. In addition, a peak at 1,700 cmappeared in the treated sample, which is the classical signature of the carbonyl bond ( Figure 1 E, red line). The ethylene glycol signature was also seen when the probe was pointed close to holes in PE caused by intact worms, but not when the probe was pointed at a distance ( Figure S1 C–E).

The formation of products after treatment with wax worm extract was also characterised by high performance liquid chromatography coupled with mass spectrometry (HPLC–MS), covering a mass/charge (m/z) range from 100 to 600 ( Figure S1 F,G). Figure S1 G shows the spectra for untreated PE (top, black) and the treated PE (bottom, red). In the samples treated with the wax worm extract three new peaks appeared at the lower end of the m/z region (110.0, 122.9 and 170.0). The chemical identity of these lighter fractions was not confirmed but their presence supports the hypothesis of PE degradation by the wax worm homogenate.

To analyse further the effect of wax worm homogenate on the PE surface, Atomic Force Microscopy (AFM) was performed ( Figure 1 F,G). After treatment with homogenate, we observed an obvious change in the topography of the PE surface ( Figure 1 G), corresponding to a significant (one-way ANOVA = 0.005) greater than 140% increase in surface roughness ( Figure S1 H and Table S1 D). These results indicate that the physical contact of the wax worm homogenate with the PE surface modified the integrity of the polymer surface.