Ideonella sakaiensis

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Ideonella sakaiensis
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Bacteria
Phylum: Pseudomonadota
Class: Betaproteobacteria
Order: Burkholderiales
Family: Comamonadaceae
Genus: Ideonella
Species:
I. sakaiensis
Binomial name
Ideonella sakaiensis
Yoshida et al. 2016 [1]

Ideonella sakaiensis is a bacterium from the genus Ideonella and family Comamonadaceae capable of breaking down and consuming the plastic polyethylene terephthalate (PET) using it as both a carbon and energy source. The bacterium was originally isolated from a sediment sample taken outside of a plastic bottle recycling facility in Sakai City, Japan. [1] [2]

Contents

Discovery

Ideonella sakaiensis was first identified in 2016 by a team of researchers led by Kohei Oda of Kyoto Institute of Technology and Kenji Miyamoto of Keio University after collecting a sample of PET-contaminated sediment at a plastic bottle recycling facility in Sakai, Japan. [1] [3] The bacteria was first isolated from a consortium of microorganisms in the sediment sample, which included protozoa and yeast-like cells. The entire microbial community was shown to mineralize 75% of the degraded PET into carbon dioxide once it had been initially degraded and assimilated by Ideonella sakaiensis. [1]

Characterization

Physical attributes

Ideonella sakaiensis is gram-negative, aerobic, and rod-shaped. Cells are motile and have a single flagellum. Colonies of I. sakaiensis are colorless, smooth, and circular. Its size varies from 0.6 to 0.8 μm in width and 1.2-1.5 μm in length. [1]

Chemical attributes

I. sakaiensis also tests positive for oxidase and catalase. The bacterium grows at a pH range of 5.5 to 9.0 (optimally at 7 to 7.5) and a temperature of 15–42 °C (59–108 °F) (optimally at 30–37 °C (86–99 °F)).

Ideonella sakaiensis adhering to PET plastic with its thin flagellum & delivering PET-degrading enzymes to the plastic's surface Ideonella Sakaiensis Eating Plastics.png
Ideonella sakaiensis adhering to PET plastic with its thin flagellum & delivering PET-degrading enzymes to the plastic's surface

Use of characteristics

This bacterium's gram negativity gives it resistant abilities and genes; this could include antibiotic resistance. The negativity also means that it has a thin cell wall and a high lipid content.[ citation needed ]

The aerobic aspect of this bacterium means that it can grow and thrive only in an environment that contains oxygen. Ideonella sakaiensis and other aerobic bacteria therefore survive in oxygen-rich soil that is moist and aerated.[ citation needed ]

The flagellum attached to this bacterium are used as motile organelles and are able to rotate and thrust the cell throughout its environment by creating motion. The bacterium was also shown to grow on the surface of polyethylene terephthalate (PET),a type of plastic, adhering with its thin flagellum. This is shown in the image to the right. The flagellum may also secrete PET-degrading enzymes onto the PET surface known as PETases.[ citation needed ]

Through phylogenetic analysis, the species was shown to be a part of the genus Ideonella, but possessed a significantly different genome than other known species in the genus, including Ideonella dechloratans and Ideonella azotifigens, thus justifying its classification as a new species. [1]

Degradation and assimilation of PET

I. sakaiensis PETase enzyme chemical mechanism PET Abbau.tif
I. sakaiensis PETase enzyme chemical mechanism

Ideonella sakaiensis adhere to PET surface and use a secreted PET hydrolase, or PETase, to degrade the PET into mono(2-hydroxyethyl)terephthalic acid (MHET), a heterodimer composed of terephthalic acid (TPA) and ethylene glycol. The PETase also degrades PET into another intermediate known as Bis-(2-hydroxyethyl) terephthalate (BHET), BHET can be converted into MHET after PET hydrolysis. [4] The I. sakaiensis PETase functions by hydrolyzing the ester bonds present in PET with high specificity. The resulting MHET is then degraded into its two monomeric constituents by a lipid-anchored MHET hydrolase enzyme, or MHETase, on the cell's outer membrane. [1] The overall mechanism of the PET plastic being broken down is exhibited in the image above. The monomeric constituents such as ethylene glycol is then taken up and used by I. sakaiensis and many other bacteria. [1] [5] The other constituent; terephthalic acid, a more recalcitrant compound, is imported into the I. sakaiensis cell via the terephthalic acid transporter protein. Once in the cell, the aromatic terephthalic acid molecule is oxidized by terephthalic acid-1,2-dioxygenase and 1,2-dihydroxy-3,5-cyclohexadiene-1,4-dicarboxylate dehydrogenase into a catechol intermediate. The catechol ring is then cleaved by PCA 3,4-dioxygenase before the compound is integrated into other metabolic pathways (e.g. TCA cycle). [1] As a result, both of the molecules derived from the PET are used by the cell to produce energy and to build necessary biomolecules. Eventually, the assimilated carbon may be mineralized to carbon dioxide and released into the atmosphere. [1]

Impact and applications

The discovery of Ideonella sakaiensis has potential importance for the degradation of PET plastics. Prior to its discovery, the only known degraders of PET were a small number of bacteria and fungi, including Fusarium solani , and no organisms were definitively known to degrade PET as a primary carbon and energy source. [1] The discovery of I. sakaiensis spurred discussion about PET biodegradation as a method of recycling and bioremediation. [1]

The wild-type bacterium is able to colonize and break down a thin (0.2 mm thickness) film of low-crystallinity (soft) PET in approximately 6 weeks, and the responsible PETase enzyme was shown to degrade high-crystallinity (hard) PET approximately 30-fold slower (180 weeks or more than 3 years) than low-crystallinity PET. [1] A large amount of manufactured PET is highly crystalline (e.g. plastic bottles), so it is thought that any prospective applications of the I. sakaiensis PETase enzyme in recycling programs will need to be preceded by genetic optimization of the enzyme. [1] [6] The MHETase enzyme could also be optimized and used in recycling or bioremediation applications in combination with the PETase enzyme. It degrades the MHET produced by the PETase into ethylene glycol and terephthalic acid. [1] Once formed, these two compounds can be further biodegraded into carbon dioxide by I. sakaiensis or other microbes, or purified and used to manufacture new PET in an industrial recycling plant setting. [1] [7]

Ideonella sakaiensis is being studied for its PET-degrading capabilities in sewage-fed fisheries. Various strains of this bacterium have been shown not to pose any threat to the growth and cultivation of fish. This species of bacterium makes effective use of PET as a source of carbon, and thrives in wastewater and plastic-polluted water ecosystems, showing its promise as a cost-effective anti-pollutant. [8]

Genetic engineering

The PET plastic-degrading enzyme of Ideonella sakaiensis known as; PETase, has been genetically modified and combined with MHETase to break down PET faster, which also degrades PEF (polyethylene furanoate) plastics. This, along with other approaches, may be useful in recycling and upcycling mixed plastics. [9] [10] [11]

Coagulation filtration system

In 2021, fifth graders Julia Stewart and Jacob Park created a coagulation filtration system concept for Toshiba's ExploraVision contest, using Ideonella sakaiensis in a process that filters, coagulates, flocculates, and sediments water in a more environmentally friendly and efficient way. [12] [13] [14] This project won the 4-6 division of ExploraVision in the United States. [12] [13]

See also

Related Research Articles

<span class="mw-page-title-main">Petrochemical</span> Chemical product derived from petroleum

Petrochemicals are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sources such as maize, palm fruit or sugar cane.

<span class="mw-page-title-main">Polyethylene</span> Most common thermoplastic polymer

Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bottles, cups, jars, etc.). As of 2017, over 100 million tonnes of polyethylene resins are being produced annually, accounting for 34% of the total plastics market.

<span class="mw-page-title-main">Polyethylene terephthalate</span> Polymer

Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, and thermoforming for manufacturing, and in combination with glass fibre for engineering resins.

<span class="mw-page-title-main">PET bottle recycling</span> Recycling of bottles made of polyethylene terephthalate

Although PET is used in several applications, as of 2022 only bottles are collected at a substantial scale. The main motivations have been either cost reduction or recycle content of retail goods. An increasing amount is recycled back into bottles, the rest goes into fibres, film, thermoformed packaging and strapping. After sorting, cleaning and grinding, 'bottle flake' is obtained, which is then processed by either:

<span class="mw-page-title-main">Dimethyl terephthalate</span> Chemical compound

Dimethyl terephthalate (DMT) is an organic compound with the formula C6H4(COOCH3)2. It is the diester formed from terephthalic acid and methanol. It is a white solid that melts to give a distillable colourless liquid.

<span class="mw-page-title-main">Low-density polyethylene</span> Chemical compound

Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was the first grade of polyethylene, produced in 1933 by Dr John C. Swallow and M.W Perrin who were working for Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization. Its manufacture employs the same method today. The EPA estimates 5.7% of LDPE is recycled in the United States. Despite competition from more modern polymers, LDPE continues to be an important plastic grade. In 2013 the worldwide LDPE market reached a volume of about US$33 billion.

<span class="mw-page-title-main">Polyester</span> Category of polymers, in which the monomers are joined together by ester links

Polyester is a category of polymers that contain one or two ester linkages in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include naturally occurring chemicals, such as in plants and insects, as well as synthetics such as polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not. Synthetic polyesters are used extensively in clothing.

PBAT is a biodegradable random copolymer, specifically a copolyester of adipic acid, 1,4-butanediol and terephthalic acid. PBAT is produced by many different manufacturers and may be known by the brand names ecoflex, Wango,Ecoworld, Eastar Bio, and Origo-Bi. It is also called poly(butylene adipate-co-terephthalate) and sometimes polybutyrate-adipate-terephthalate or even just "polybutyrate". It is generally marketed as a fully biodegradable alternative to low-density polyethylene, having many similar properties including flexibility and resilience, allowing it to be used for many similar uses such as plastic bags and wraps. The structure is a random-block polymer consisting of butanediol–adipic acid and butanediol-terephthalic acid blocks.

<span class="mw-page-title-main">Cyclohexanedimethanol</span> Chemical compound

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Ideonella is a genus of bacteria in the family Comamonadaceae.

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<span class="mw-page-title-main">PETase</span> Class of enzymes

PETases are an esterase class of enzymes that catalyze the breakdown (via hydrolysis) of polyethylene terephthalate (PET) plastic to monomeric mono-2-hydroxyethyl terephthalate (MHET). The idealized chemical reaction is:

2-Hydroxyethyl terephthalic acid is an organic compound with the formula HOC2H4O2CC6H4CO2H. It is the monoester of terephthalic acid and ethylene glycol. The compound is a precursor to poly(ethylene terephthalate) (PET), a polymer that is produced on a large scale industrially. 2-Hydroxyethyl terephthalic acid is a colorless solid that is soluble in water and polar organic solvents. Near neutral pH, 2-hydroxyethyl terephthalic acid converts to 2-hydroxyethyl terephthalate, HOC2H4O2CC6H4CO2−.

Kohei Oda is a Japanese microbiologist and an emeritus professor at Kyoto Institute of Technology. He is known for his work on bacterial discovery and bacterial metabolism. In particular, he led a team of Japanese scientists in the discovery of plastic-degrading bacteria, Ideonella sakaiensis, in 2016.

<span class="mw-page-title-main">MHETase</span>

The enzyme MHETase is a hydrolase, which was discovered in 2016. It cleaves 2-hydroxyethyl terephthalic acid, the PET degradation product by PETase, to ethylene glycol and terephthalic acid. This pair of enzymes, PETase and MHETase, enable the bacterium Ideonella sakaiensis to live on the plastic PET as sole carbon source.

<span class="mw-page-title-main">Plastic degradation by marine bacteria</span> Ability of bacteria to break down plastic polymers

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References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Yoshida S, Hiraga K, Takehana T, Taniguchi I, Yamaji H, Maeda Y, et al. (March 2016). "A bacterium that degrades and assimilates poly(ethylene terephthalate)". Science. 351 (6278): 1196–1199. Bibcode:2016Sci...351.1196Y. doi:10.1126/science.aad6359. PMID   26965627. S2CID   31146235.
  2. ↑ "Discovery of a Bacterium that Degrades and Assimilates Poly(ethylene terephthalate) could Serve as a Degradation and/or Fermentation Platform for Biological Recycling of PET Waste Products" (PDF). Kyoto Institute of Technology (Press release). 30 March 2016.
  3. ↑ Ong, Sandy (24 August 2023). "The living things that feast on plastic". Knowable Magazine | Annual Reviews. doi: 10.1146/knowable-082423-1 .
  4. ↑ Puspitasari N, Tsai SL, Lee CK (April 2021). "Class I hydrophobins pretreatment stimulates PETase for monomers recycling of waste PETs" (PDF). International Journal of Biological Macromolecules. 176: 157–164. doi:10.1016/j.ijbiomac.2021.02.026. PMID   33561457. S2CID   231865499.
  5. ↑ Pearce BA, Heydeman MT (1 May 1980). "Metabolism of Di(ethylene glycol) [2-(2'-Hydroxyethoxy)ethanol] and Other Short Poly(ethylene glycol)s by Gram-negative Bacteria". Microbiology. 118 (1): 21–27. doi: 10.1099/00221287-118-1-21 . ISSN   1350-0872.
  6. ↑ Coghlan A. "Bacteria found to eat PET plastics could help do the recycling". New Scientist. Retrieved 18 March 2016.
  7. ↑ Al-Sabagh AM, Yehia FZ, Eshaq G, Rabie AM, El Metwally AE (March 2016). "Greener routes for recycling of polyethylene terephthalate". Egyptian Journal of Petroleum. 25 (1): 53–64. Bibcode:2016EgyJP..25...53A. doi: 10.1016/j.ejpe.2015.03.001 .
  8. ↑ Misra J (April 2020). "Managing Wastewater Using Plastic Eating Bacteria - A Sustainable Solution for Sewage Fed Fisheries". Journal of the Indian Chemical Society. 97 (4): 513–519.
  9. ↑ Carrington D (28 September 2020). "New super-enzyme eats plastic bottles six times faster". The Guardian. Retrieved 12 October 2020.
  10. ↑ "Plastic-eating enzyme 'cocktail' heralds new hope for plastic waste". phys.org. Retrieved 12 October 2020.
  11. ↑ Knott BC, Erickson E, Allen MD, Gado JE, Graham R, Kearns FL, et al. (October 2020). "Characterization and engineering of a two-enzyme system for plastics depolymerization". Proceedings of the National Academy of Sciences of the United States of America. 117 (41): 25476–25485. Bibcode:2020PNAS..11725476K. doi: 10.1073/pnas.2006753117 . PMC   7568301 . PMID   32989159.
  12. 1 2 "Eight Student Teams Named National Winners of 29th Annual ExploraVision Challenge". news.toshiba.com. Retrieved 3 December 2021.
  13. 1 2 "Introducing the 2021 ExploraVision National Winners". www.exploravision.org. 18 May 2021. Retrieved 3 December 2021.
  14. ↑ "Coagulation Filtration System". ExploraVision.PPT te. Retrieved 3 December 2021.
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