Shosuke Yoshida ,
Could a new plastic-eating bacteria help
combat this pollution scourge?
Scientists have discovered a species of
bacteria capable of breaking down commonly used PET plastic
but remain unsure of its potential applications
PET makes up almost one sixth of the world’s annual plastic
production but only about half is ever collected for recycling.
Nature has begun to fight back against the vast piles of filth
dumped into its soils, rivers and oceans by evolving a
plastic-eating bacteria – the first known to science.
In a report published in the journal Science, a team of Japanese
researchers described a species of bacteria that can break the
molecular bonds of one of the world’s most-used plastics -
polyethylene terephthalate, also known as PET or polyester.
The Japanese research team sifted through hundreds of samples of
PET pollution before finding a colony of organisms using the
plastic as a food source.
Further tests found the bacteria almost completely degraded
low-quality plastic within six weeks. This was voracious when
compared to other biological agents; including a related bacteria,
leaf compost and a fungus enzyme recently found to have an
appetite for PET.
“This is the first rigorous study – it appears to be very
carefully done – that I have seen that shows plastic being
hydrolyzed [broken down] by bacteria,” said Dr Tracy Mincer, a
researcher at Woods Hole Oceanographic Institution.
The molecules that form PET are bonded very strongly, said Prof
Uwe Bornscheuer in an accompanying comment piece in Science.
“Until recently, no organisms were known to be able to decompose
In a Gaian twist, initial genetic examination revealed the
bacteria, named Ideonella sakaiensis 201-F6, may have evolved
enzymes specifically capable of breaking down PET in response to
the accumulation of the plastic in the environment in the past 70
Such rapid evolution was possible, said Enzo Palombo, a professor
of microbiology at Swinburne University, given that microbes have
an extraordinary ability to adapt to their surroundings. “If you
put a bacteria in a situation where they’ve only got one food
source to consume, over time they will adapt to do that,” he said.
“I think we are seeing how nature can surprise us and in the end
the resiliency of nature itself,” added Mincer.
The bacteria took longer to eat away highly crystallised PET,
which is used in plastic bottles. That means the enzymes and
processes would need refinement before they could be useful for
industrial recycling or pollution clean-up.
“It’s difficult to break down highly crystallised PET,” said Prof
Kenji Miyamoto from Keio University, one of the authors of the
study. “Our research results are just the initiation for the
application. We have to work on so many issues needed for various
applications. It takes a long time,” he said.
A third of all plastics end up in the environment and 8m tonnes
end up in the ocean every year, creating vast accumulations of
PET makes up almost one-sixth of the world’s annual plastic
production of 311m tons. Despite PET being one of the more
commonly recycled plastics, the World Economic Forum (WEF) reports
that only just over half is ever collected for recycling and far
less actually ends up being reused.
Advances in biodegradable plastics and recycling offer hope for
the future, said Bornscheuer, “but [this] does not help to get rid
of the plastics already in the environment”.
However the potential applications of the discovery remain
unclear. The most obvious use would be as a biological agent in
nature, said Palombo. Bacteria could be sprayed on the huge
floating trash heaps building up in the oceans. This method is
most notably employed to combat oil spills.
This particular bacteria would not be useful for this process as
it only consumes PET, which is too dense to float on water. But
Bornscheuer said the discovery could open the door to the
discovery or manufacture of biological agents able to break down
Palombo said the discovery suggested that other bacteria may have
already evolved to do this job and simply needed to be found.
“I would not be surprised if samples of ocean plastics contained
microbes that are happily growing on this material and could be
isolated in the same manner,” he said.
But Mincer said breaking down ocean rubbish came with dangers of
its own. Plastics often contain additives that can be toxic when
released. WEF estimates that the 150m tonnes of plastic currently
in the ocean contain roughly 23m tonnes of additives.
“Plastic debris may have been less toxic in the whole unhydrolyzed
form where it would ultimately have been buried in the sediments
on a geological timescale,” said Mincer.
Beyond dealing with the plastic already fouling up the
environment, the bacteria could potentially be used in industrial
“Certainly, the use of these microbes or enzymes could play a role
in remediation of plastic in a controlled reactor,” said Mincer.
Miyamoto’s team suggested that the environmentally-benign
constituents left behind by the bacteria could be the same ones
from which the plastic is formed. If this were true and a process
could be developed to isolate them, Bornscheuer said: “This could
provide huge savings in the production of new polymer without the
need for petrol-based starting materials.” According to the WEF,
6% of global oil production is devoted to the production of
But the plastics industry said the potential for a new biological
process to replace or augment the current mechanical recycling
process was very small.
“PET is 100% recyclable,” said Mike Neal, the chairman of the
Committee of PET Manufacturers in Europe. “I expect that a
biodegradation system would require a similar engineering process
to chemical depolymerisation and as such is unlikely to be
economically viable,” he said.
Science 11 Mar 2016: Vol. 351, Issue
6278, pp. 1196-1199
A bacterium that degrades and assimilates
Bacteria isolated from outside a bottle-recycling
facility can 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. Yoshida et al. show how the biodegradation of
plastics by specialized bacteria could be a viable bioremediation
strategy (see the Perspective by Bornscheuer). 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.
Shosuke Yoshida, et al.
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, we 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
AROMATIC POLYESTER DECOMPOSITION ENZYME AND METHOD FOR
DECOMPOSING AROMATIC POLYESTER USING SAID ENZYME
[ PDF ]
Inventor: MIYAMOTO KENJI, et al.
Provided is an enzyme for hydrolyzing an aromatic polyester resin
such as PET resin, and provided is a method for decomposing an
aromatic polyester resin such as PET resin using said enzyme. An
aromatic polyester such as polyethylene terephthalate (PET) can be
decomposed by an aromatic polyester decomposition enzyme composed
of an amino acid sequence represented by sequence nos. 2 or 4 of
the sequence listing. Monohydryoxy ethyl terephthalate (MHET)
produced by enzymatic decomposition of an aromatic polyester such
as polyethylene terephthalate (PET) can be furthermore decomposed
to completely form a monomer using an enzyme having MHET
hydrolytic activity composed of the polyester decomposition enzyme
and an amino acid sequence represented by sequence nos. 10 or 12
of the sequence listing.
Biochim Biophys Acta. 2015
Structural and functional studies of a Fusarium oxysporum
cutinase with polyethylene terephthalate modification
Dimarogona M., et al.
Cutinases are serine hydrolases that degrade cutin, a polyester of
fatty acids that is the main component of plant cuticle. These
biocatalysts have recently attracted increased biotechnological
interest due to their potential to modify and degrade polyethylene
terephthalate (PET), as well as other synthetic polymers.
A cutinase from the mesophilic fungus Fusarium oxysporum, named
FoCut5a, was expressed either in the cytoplasm or periplasm of
Escherichia coli BL21. Its X-ray structure was determined to 1.9Å
resolution using molecular replacement. The activity of the
recombinant enzyme was tested on a variety of synthetic esters and
The highest production of recombinant FoCut5a was achieved using
periplasmic expression at 16°C. Its crystal structure is highly
similar to previously determined Fusarium solani cutinase
structure. However, a more detailed comparison of the surface
properties and amino acid interactions revealed differences with
potential impact on the biochemical properties of the two enzymes.
FoCut5a showed maximum activity at 40°C and pH 8.0, while it was
active on three p-nitrophenyl synthetic esters of aliphatic acids
(C(2), C(4), C(12)), with the highest catalytic efficiency for the
hydrolysis of the butyl ester. The recombinant cutinase was also
found capable of hydrolyzing PET model substrates and synthetic
The present work is the first reported expression and crystal
structure determination of a functional cutinase from the
mesophilic fungus F. oxysporum with potential application in
surface modification of PET synthetic polymers.
FoCut5a could be used as a biocatalyst in industrial applications
for the environmentally-friendly treatment of synthetic polymers.
Ideonella sakaiensis is a bacterium from the genus Ideonella
and family Comamonadaceae capable of breaking down PET plastic
which was isolated from outside a plastic bottle recycling
Ideonella sakaiensis was identified in 2016 by a team of
researchers from Kyoto Institute of Technology and Keio University
after collecting samples of PET debris in search for bacteria that
relied on the plastic for carbon growth. The bacterium first uses
PETase, an enzyme that works with water, to break down the PET
plastic. It then breaks it down further using MHETase, another
enzyme that further reacts with water to break down the plastics
into terephthalic acid and ethylene glycol.
The discovery of Ideonella sakaiensis has potential importance
for the recycling process of PET plastics. Prior to its discovery,
the only known consumers of PET were a small number of fungi
including Pestalotiopsis microspora, and knowledge of the new
species has spurred discussion about biodegradation as a method of
recycling. The bacterium can currently break down a thin film
of PET in a little over six weeks, so it is thought that any
prospective applications in mass recycling programs will have to
be preceded by enhancement of its abilities through genetic
I. sakaiensis is Gram-negative, aerobic, and rod-shaped. It
does not form spores. The individual cells of the organism are
motile and have a single flagellum. I. sakaiensis tests positive
for oxidase and catalase. The bacterium grows at a pH range of 5.5
to 9.0 (optimally 7 to 7.5) and a temperature of 15-42 °C
(optimally at 30-37 °C). Through phylogenetic analysis, the
species was shown to be affiliated to the genus Ideonella, and
also related to Ideonella dechloratans and Ideonella azotifigens,
justifying its scientific classification.
Colonies of I. sakaiensis are colorless, smooth, and
EC number 220.127.116.11
Alt. names PET hydrolase, poly(ethylene
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PDB structures RCSB PDB PDBe PDBsum
PETase is an enzyme discovered in 2016 from a Japanese rubbish
dump from Ideonella sakaiensis bacteria. PETase breaks down
PET-plastic to monomeric mono-2-hydroxyethyl terephthalate (MHET)
molecules. MHET is broken down in these bacteria to hydroxyethyl
terephthalate with the help of MHETase enzyme. Hydroxyethyl
terephthalate breaks down in water to terephthalic acid and
ethylene glycol, which are environmentally harmless as they are
broken down further to produce carbon dioxide and water.
The reaction catalyzed by PETase is (n is the number of
monomers in the PET polymer):...
In 2018, John McGeehan co-led an international team (the
University of Portsmouth and the U.S. Department of Energy's
National Renewable Energy Laboratory) that managed to genetically
alter PETase making it 20% more efficient, and raising the
possibility of further efficiency gains. Their aim is to
use PETase to recycle the coloured polyethylene terephthalate
(PET) plastic used in soft drink bottles and turn it back into
easily reusable clear plastic.
Professor John McGeehan, Professor of Structural Biology at the
University of Plymouth and one of the scientists leading the
study, made the following remarks on the enzyme improvement:
"Although the improvement is modest, this unanticipated discovery
suggests that there is room to further improve these enzymes,
moving us closer to a recycling solution for the ever-growing
mountain of discarded plastics."
Yoshida, Shosuke; Hiraga, Kazumi; Takehana, Toshihiko;
Taniguchi, Ikuo; Yamaji, Hironao; Maeda, Yasuhito; Toyohara,
Kiyotsuna; Miyamoto, Kenji; Kimura, Yoshiharu (2016-03-11). "A
bacterium that degrades and assimilates poly(ethylene
terephthalate)". Science. 351 (6278): 1196–1199.
doi:10.1126/science.aad6359. ISSN 0036-8075. PMID 26965627.
Tanasupawat, Somboon; Takehana, Toshihiko; Yoshida, Shosuke;
Hiraga, Kazumi; Oda, Kohei (August 2016). "Ideonella sakaiensis
sp. nov., isolated from a microbial consortium that degrades
poly(ethylene terephthalate)". International Journal of Systematic
and Evolutionary Microbiology. 66 (8): 2813–2818.
doi:10.1099/ijsem.0.001058. ISSN 1466-5034. PMID 27045688.
"BRENDA - Information on EC 18.104.22.168 - poly(ethylene
terephthalate) hydrolase". www.brenda-enzymes.org.
Austin, Harry P.; Allen, Mark D.; Donohoe, Bryon S.; Rorrer,
Nicholas A.; Kearns, Fiona L.; Silveira, Rodrigo L.; Pollard,
Benjamin C.; Dominick, Graham; Duman, Ramona (2018-04-17).
"Characterization and engineering of a plastic-degrading aromatic
polyesterase". Proceedings of the National Academy of Sciences.
doi:10.1073/pnas.1718804115. ISSN 0027-8424. PMID 29666242.
Carrington, Damian (16 April 2018). "Scientists accidentally
create mutant enzyme that eats plastic bottles". the Guardian.
Editorial, Reuters. "Plastic-eating enzyme holds promise in
fighting pollution - scientists". reuters.com.
"Scientists accidentally discovered a mutant enzyme that could
help the world eliminate plastic waste".
Ideonella sakaiensis sp. nov., isolated
from a microbial consortium that degrades poly(ethylene
Somboon Tanasupawat, et al
[ PDF ]
Novel, esterase, fungus capable of producing the same and
method for producing the same
Inventor(s): SHINOHARA MAKOTO, et al.
The present invention provides a novel esterase derived from
Ideonella sp. 0-0013 strain (FERM BP-08660) having the following
properties: (1) function, substrate specificity: hydrolyzes methyl
3-hydroxypalmitate to generate 3-hydroxypalmitic acid and
methanol; (2) optimal temperature for functioning: 37 DEG C.; (3)
optimal pH and stable pH range: pH 7 or more to pH 10 or less; (4)
temperature stability: 97% of the enzyme is stable at 43 DEG C.;
(5) inhibition, activation, and stabilization: activated by sodium
ion and potassium ion, and inhibited by strontium ion, iron ion
(divalent), and methyl palmitate; (6) molecular weight: about
46,500 Da (by SDS-PAGE), about 41,000 Da (by a gel filtration
method); and (7) isoelectric point: pI 4 (by polyacrylamide gel
isoelectric focusing method); a microorganism producing the
enzyme; and a method of producing the enzyme.
Structural insight into molecular mechanism
of PET degradation
KAIST team newly suggests a molecular
mechanism showing superior degradability of PET
A KAIST metabolic engineering research team has newly suggested a
molecular mechanism showing superior degradability of poly
ethylene terephthalate (PET).
This is the first report to simultaneously determine the 3D
crystal structure of Ideonella sakaiensis PETase and develop the
new variant with enhanced PET degradation.
Recently, diverse research projects are working to address the
non-degradability of materials. A poly ethylene terephthalate
(PET)-degrading bacterium called Ideonella sakaiensis was recently
identified for the possible degradation and recycling of PET by
Japanese team in Science journal (Yoshida et al., 2016). However,
the detailed molecular mechanism of PET degradation has not been
The team under Distinguished Professor Sang Yup Lee of the
Department of Chemical and Biomolecular Engineering and the team
under Professor Kyung-Jin Kim of the Department of Biotechnology
at Kyungpook National University conducted this research. The
findings were published in Nature Communications on January 26.
This research predicts a special molecular mechanism based on the
docking simulation between PETase and a PET alternative mimic
substrate. Furthermore, they succeeded in constructing the variant
for IsPETase with enhanced PET-degrading activity using
structural-based protein engineering.
It is expected that the new approaches taken in this research can
be background for further study of other enzymes capable of
degrading not only PET but other plastics as well.
PET is very important source in our daily lives. However, PET
after use causes tremendous contamination issues to our
environment due to its non-biodegradability, which has been a
major advantage of PET. Conventionally, PET is disposed of in
landfills, using incineration, and sometimes recycling using
chemical methods, which induces additional environmental
pollution. Therefore, a new development for highly-efficient PET
degrading enzymes is essential to degrade PET using bio-based
Recently, a new bacterial species, Ideonella sakaiensis, which can
use PET as a carbon source, was isolated. The PETase of I.
sakaiensis (IsPETase) can degrade PET with relatively higher
success than other PET-degrading enzymes. However, the detailed
enzyme mechanism has not been elucidated, hindering further
The research teams investigated how the substrate binds to the
enzyme and which differences in enzyme structure result in
significantly higher PET degrading activity compared with other
cutinases and esterases, which make IsPETase highly attractive for
industrial applications toward PET waste recycling.
Based on the 3D structure and related biochemical studies, they
successfully predicted the reasons for extraordinary PET degrading
activity of IsPETase and suggested other enzymes that can degrade
PET with a newly-classified phylogenetic tree. The team proposed
that 4 MHET moieties are the most properly matched substrates due
to a cleft on structure even with the 10-20-mers for PET. This is
meaningful in that it is the first docking simulation between
PETase and PET, not its monomer.
Furthermore, they succeeded in developing a new variant with much
higher PET-degrading activity using a crystal structure of this
variant to show that the changed structure is better to
accommodate PET substrates than wild type PETase, which will lead
to developing further superior enzymes and constructing platforms
for microbial plastic recycling.
Professor Lee said, "Environmental pollution from plastics remains
one of the greatest challenges worldwide with the increasing
consumption of plastics. We successfully constructed a new
superior PET-degrading variant with the determination of a crystal
structure of PETase and its degrading molecular mechanism. This
novel technology will help further studies to engineer more
superior enzymes with high efficiency in degrading. This will be
the subject of our team's ongoing research projects to address the
global environmental pollution problem for next generation."
Nature Communicationsvolume 9, Article number: 382 (2018)
Structural insight into molecular mechanism
of poly(ethylene terephthalate) degradation
Seongjoon Joo, et al.
Plastics, including poly(ethylene terephthalate) (PET), possess
many desirable characteristics and thus are widely used in daily
life. However, non-biodegradability, once thought to be an
advantage offered by plastics, is causing major environmental
problem. Recently, a PET-degrading bacterium, Ideonella
sakaiensis, was identified and suggested for possible use in
degradation and/or recycling of PET. However, the molecular
mechanism of PET degradation is not known. Here we report the
crystal structure of I. sakaiensis PETase (IsPETase) at 1.5 Å
resolution. IsPETase has a Ser–His-Asp catalytic triad at its
active site and contains an optimal substrate binding site to
accommodate four monohydroxyethyl terephthalate (MHET) moieties of
PET. Based on structural and site-directed mutagenesis
experiments, the detailed process of PET degradation into MHET,
terephthalic acid, and ethylene glycol is suggested. Moreover,
other PETase candidates potentially having high PET-degrading
activities are suggested based on phylogenetic tree analysis of 69
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