permaculture

[Lawrence London <lfljvenaura@gmail.com>]

Caterpillar found to eat shopping bags, suggesting biodegradable solution
to plastic pollution
April 24, 2017
https://phys.org/news/2017-04-caterpillar-bags-biodegradable-solution-plastic.html

[image: Caterpillar found to eat shopping bags, suggesting biodegradable
solution to plastic pollution]
<https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hires/2017/caterpillarf.jpg>
Wax worm specimens in a Petri dish. Credit: César Hernández/CSIC

Scientists have found that a caterpillar commercially bred for fishing bait
has the ability to biodegrade polyethylene: one of the toughest and most
used plastics, frequently found clogging up landfill sites in the form of
plastic shopping bags.

The wax worm, the larvae of the common insect Galleria mellonella, or
greater wax moth, is a scourge of beehives across Europe. In the wild, the
worms live as parasites in bee colonies. Wax moths lay their eggs inside
hives where the worms hatch and grow on beeswax - hence the name.

A chance discovery occurred when one of the scientific team, Federica
Bertocchini, an amateur beekeeper, was removing the parasitic pests from
the honeycombs in her hives. The worms were temporarily kept in a typical
plastic shopping bag that became riddled with holes.

Bertocchini, from the Institute of Biomedicine and Biotechnology of
Cantabria (CSIC), Spain, collaborated with colleagues Paolo Bombelli and
Christopher Howe at the University of Cambridge's Department of
Biochemistry to conduct a timed experiment.

Around a hundred wax worms were exposed to a plastic bag from a UK
supermarket. Holes started to appear after just 40 minutes, and after 12
hours there was a reduction in plastic mass of 92mg from the bag.

Scientists say that the degradation rate is extremely fast compared to
other recent discoveries, such as bacteria reported last year to biodegrade
some plastics at a rate of just 0.13mg a day.
Plastic biodegraded by 10 worms in 30 minutes. Credit: César Hernández/CSIC

"If a single enzyme is responsible for this chemical process, its
reproduction on a large scale using biotechnological methods should be
achievable," said Cambridge's Paolo Bombelli, first author of the study
published today in the journal *Current Biology*.

"This discovery could be an important tool for helping to get rid of the
polyethylene <https://phys.org/tags/polyethylene/> plastic waste
accumulated in landfill sites <https://phys.org/tags/landfill+sites/> and
oceans."

Polyethylene is largely used in packaging, and accounts for 40% of total
demand for plastic products across Europe - where up to 38% of plastic is
discarded in landfills. People around the world use around a trillion
plastic bags every single year.

Generally speaking, plastic is highly resistant to breaking down, and even
when it does the smaller pieces choke up ecosystems without degrading. The
environmental toll is a heavy one.

Yet nature may provide an answer. The beeswax on which wax worms grow is
composed of a highly diverse mixture of lipid compounds: building block
molecules of living cells, including fats, oils and some hormones.

While the molecular detail of wax biodegradation requires further
investigation, the researchers say it is likely that digesting beeswax and
polyethylene involves breaking similar types of chemical bonds.
[image: Caterpillar found to eat shopping bags, suggesting biodegradable
solution to plastic pollution]
<https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hires/2017/2-caterpillarf.jpg>
A close-up of wax worm next to biodegraded holes in a polyethylene plastic
shopping bag from a UK supermarket as used in the experiment. Credit: Paolo
Bombelli

"Wax is a polymer, a sort of 'natural plastic,' and has a chemical
structure not dissimilar to polyethylene," said CSIC's Bertocchini, the
study's lead author.

The researchers conducted spectroscopic analysis to show the chemical bonds
<https://phys.org/tags/chemical+bonds/> in the plastic were breaking. The
analysis showed the worms transformed the polyethylene into ethylene
glycol, representing un-bonded 'monomer' molecules.

To confirm it wasn't just the chewing mechanism of the caterpillars
degrading the plastic, the team mashed up some of the worms and smeared
them on polyethylene bags, with similar results.

"The caterpillars are not just eating the plastic without modifying its
chemical make-up. We showed that the polymer chains in polyethylene plastic
are actually broken by the wax worms <https://phys.org/tags/worms/>," said
Bombelli.

"The caterpillar produces something that breaks the chemical bond, perhaps
in its salivary glands or a symbiotic bacteria in its gut. The next steps
for us will be to try and identify the molecular processes in this reaction
and see if we can isolate the enzyme responsible."

As the molecular details of the process become known, the researchers say
it could be used to devise a biotechnological solution on an industrial
scale for managing polyethylene waste.

Added Bertocchini: "We are planning to implement this finding into a viable
way to get rid of plastic waste, working towards a solution to save our
oceans, rivers, and all the environment from the unavoidable consequences
of plastic <https://phys.org/tags/plastic/> accumulation."


Read more at:
https://phys.org/news/2017-04-caterpillar-bags-biodegradable-solution-plastic.html#jCp

Evidence of Polyethylene Biodegradation by Bacterial Strains from the Guts
of Plastic-Eating Waxworms - Environmental Science & Technology (ACS
Publications)
http://pubs.acs.org/doi/abs/10.1021/es504038a
Evidence of Polyethylene Biodegradation by Bacterial Strains from the Guts
of Plastic-Eating Waxworms
Jun Yang <http://pubs.acs.org/author/Yang%2C+Jun>*
<http://pubs.acs.org/doi/abs/10.1021/es504038a#cor1>†, Yu Yang
<http://pubs.acs.org/author/Yang%2C+Yu>†, Wei-Min Wu
<http://pubs.acs.org/author/Wu%2C+Wei-Min>‡, Jiao Zhao
<http://pubs.acs.org/author/Zhao%2C+Jiao>§, and Lei Jiang
<http://pubs.acs.org/author/Jiang%2C+Lei>†
† Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology
of Ministry of Education, School of Chemistry and Environment, Beihang
University, Beijing 100191, P. R. China
‡ Department of Civil and Environmental Engineering, William & Cloy Codiga
Resource Recovery Research Center, Center for Sustainable Development &
Global Competitiveness, Stanford University, Stanford, California
94305-4020, United States
§ Shenzhen Key Laboratory of Bioenergy, BGI-Shenzhen, Shenzhen, Guangdong
518083, P. R. China
Environ. Sci. Technol., 2014, 48 (23), pp 13776–13784
*DOI: *10.1021/es504038a
Publication Date (Web): November 10, 2014
Copyright © 2014 American Chemical Society
*Phone/Fax: 86-10-8233-8552. E-mail: yangjun@buaa.edu.cn. Corresponding
author address: School of Chemistry and Environment, Beihang University
(BUAA), 37 Xueyuan Road, Beijing 100191, P. R. China.
Abstract
[image: Abstract Image]

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 (0.3–0.4 μm in depth), 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 approximately 6.1 ± 0.3% and 10.7 ± 0.2% of the PE films (100 mg),
respectively, 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.


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