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Scientists have discovered several organisms that can digest plastic.
PE comprises a linear backbone of carbon atoms (Figure S1B), 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-1, 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 cm-2 day-1) 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.
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 S1A). Figure 1A,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 S1C and Table S1B,C). This corresponds to an average degradation rate of 0.23 mg cm-2 h-1, which is markedly higher than the rate of PET biodegradation by a microbial consortium recently reported .
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Amazing! And if they can identify the chemical process the caterpillars use to break down the plastic, we'll have a solution for the tons of plastic waste that's polluting the environment!
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