Ideonella sakaiensis- Plastic eating bacteria

Ideonella sakaiensis- Plastic eating bacteria

Today the use of plastic and the pollutants has been the global threat. It has created an impact on the terrestrial as well as the marine ecosystem. Though the use of plastic has to comfort our living style, the lack of proper management has created pollution in nature. Recently, researchers from Japan have isolated the plastic-eating bacterium which is known as “Ideonella sakaiensis“

Ideonella sakaiensis

• In 2016, it was identified by the Kyoto Institute of Technology and Kenji Miyamoto of Keio University in Japan.
• It can use plastic poly (ethylene terephthalate) (PET) as a sole source of carbon and energy.
• It was isolated from the sediment sample outside of the plastic bottle recycling facility.
• PET is made from ethylene glycol and dimethyltryptamine (DMT)
• Both of these constituents are made from crude oil.
• Ideonella sakaiensis is able to break down into its two constituents.

Image Source: Wikipedia and Depositphotos

Scientific Classification of Ideonella sakaiensis– Plastic eating bacteria

• Domain: Bacteria
• Phylum: Proteobacteria
• Class: Betaproteobacteria
• Order: Burkholderiales
• Family: Comamonadaceae
• Genus: Ideonella
• Species: sakaiensis

Characteristics of Ideonella sakaiensis– Plastic eating bacteria

• Gram-negative
• Aerobic
• Rod-shaped
• Non-spore forming
• Motile
• Having single flagellum
• Catalase positive
• Oxidase positive
• pH 5.5-9.0 (optimum 7-7.5)
• Temperature 15-42 °C (optimum 30-37 °C)
• shown to grow on PET surface in a community with I. sakaiensis cells with the help of thin appendages
• The G+C content of genomic DNA was 70.4 mol%
• Strain: 201-F6
• no growth with 3% (w/v) NaCl or at 45 °C

Colony characteristics

• circular, smooth, non-pigmented or creamy, raised, translucent, the entire margin of 0.5-1.0 mm in diameter after incubation at 30°C on NBRC no.802 agar medium for 2 days

Enzymes

PETase or PET hydrolase 

• Hydrolyze the ester bonds in PET into mono (2-hydroxyethyl) terephthalic acid (MHET)

MHETase 

• It is a lipid-anchored MHET hydrolase enzyme present on the cells outer membrane
• Hydrolyze the MHET into two monomeric constituents

Mode of action

• PETase converts PET into mono-(2-hydroxyethyl) terephthalate acid (MHET), terephthalate (TPA), and bis (2-hydroxyethyl) TPA (PHET). Then MHETase converts MHET into ethylene glycol and TPA. Then the products can be easily broken by other micro-organisms with CO2 and water as the final result.

Applications

• Degradation of PET plastics
• Effective for recycling and bioremediation

Limitations

• Ideonella sakaiensis breaks only PET. Other kinds of plastic like polyethylene, polypropylene, and PVC do exist in nature.

Challenges

• The process is so slow. It takes about 6 weeks at 30°C to fully degrade a thumb-nail sized piece of PET.
• For industrial purposes, there are a number of practical problems

Future

Despite the limitations and challenges, we can hope that with the use of genetic engineering such enzymes may be manipulated and its production can be done on large scale. Further research may be done regarding the enzymes for the degradation of plastic other than PET.

References

1. https://en.m.wikipedia.org/wiki/Ideonella_sakaiensis
2. https://www.dtu.dk/english/news/2019/09/eng
3. https://www.microbiologyresearch.org/content/journal/ijsem/10.1099

Sources

• 3% – https://www.ncbi.nlm.nih.gov/pubmed/27045688
• 2% – https://www.sciencedirect.com/science/article/pii/S073497501530046X
• 2% – https://www.researchgate.net/profile/Kohei_Oda/publication/299771533_Ideonella_sakaiensis_sp_nov_isolated_from_a_microbial_consortium_that_degrades_PET/links/5a97c73b0f7e9ba42975639a/Ideonella-sakaiensis-sp-nov-isolated-from-a-microbial-consortium-that-degrades-PET.pdf?origin=publication_detail
• 1% – https://www.heise.de/forum/heise-online/News-Kommentare/Verbessertes-Bakterien-Enzym-verdaut-Plastikflaschen/In-was-wird-das-PET-recyclet/posting-32226220/show/
• 1% – https://www.encyclopedia.com/science-and-technology/biology-and-genetics/genetics-and-genetic-engineering/genetic-engineering
• 1% – https://ourworldindata.org/
• 1% – https://en.wikipedia.org/wiki/Noviherbaspirillum_suwonense
• 1% – http://www.ijesd.org/vol7/749-A707.pdf

Ideonella sakaiensis- Plastic eating bacteria