Bacteria isolated from outside a bottle-recycling facility has been found to break down and metabolize plastic.
The proliferation of plastics in consumer products, from bottles to clothing, has resulted in the release of countless tons of plastics into the environment. The findings, published in the academic journal ‘Science‘ show how the biodegradation of plastics by specialized bacteria could be a viable bioremediation strategy. The new species, Ideonella sakaiensis, breaks down the plastic by using two enzymes to hydrolyze, PET and a primary reaction intermediate, eventually yielding basic building blocks for growth.
Poly(ethylene terephthalate) (PET) is used extensively worldwide in plastic products, and its accumulation in the environment has become a global concern. Because the ability to enzymatically degrade PET has been thought to be limited to a few fungal species, biodegradation is not yet a viable remediation or recycling strategy. By screening natural microbial communities exposed to PET in the environment, researchers have isolated a novel bacterium, Ideonella sakaiensis 201-F6, that is able to use PET as its major energy and carbon source. When grown on PET, this strain produces two enzymes capable of hydrolyzing PET and the reaction intermediate, mono(2-hydroxyethyl) terephthalic acid. Both enzymes are required to enzymatically convert PET efficiently into its two environmentally benign monomers, terephthalic acid and ethylene glycol.
Polyethylene (PE) has been considered nonbiodegradable for decades. Although the biodegradation of PE by bacterial cultures has been occasionally described, valid evidence of PE biodegradation has remained limited in the literature. We found that waxworms, or Indian mealmoths (the larvae of Plodia interpunctella), were capable of chewing and eating PE films. Two bacterial strains capable of degrading PE were isolated from this worm’s gut, Enterobacter asburiae YT1 and Bacillus sp. YP1.
Over a 28-day incubation period of the two strains on PE films, viable biofilms formed, and the PE films’ hydrophobicity decreased. Obvious damage, including pits and cavities, was observed on the surfaces of the PE films using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The formation of carbonyl groups was verified using X-ray photoelectron spectroscopy (XPS) and microattenuated total reflectance/Fourier transform infrared (micro-ATR/FTIR) imaging microscope. Suspension cultures of YT1 and YP1 (108 cells/mL) were able to degrade the PE films over a 60-day incubation period.
The molecular weights of the residual PE films were lower, and the release of 12 water-soluble daughter products was also detected. The results demonstrated the presence of PE-degrading bacteria in the guts of waxworms and provided promising evidence for the biodegradation of PE in the environment.
While plastic eating bacteria and worms is promising, I would be remiss in saying that we need to curb our obsession with plastic. We need viable alternatives so that the issue of how to get rid of it is no longer a problem. The invention of plastic used to be seen as a miracle solution to making our lives easier. But, as it turns out plastic is becoming one of the biggest problems we face for the future of our planet and our children.
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