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Plastic pollution is one of the major contributors to pollution in the world, we are all aware of how it jeopardizes the lives of plant and animal life due to it being non-biodegradable. As a scientist it is only natural to be the solution to pollution, therefore I have chosen Ideonella sakainesis as my adopted bacterium. Ideonella sakaiensis has the ability to break down PET that is found in plastics into monomers through enzymatic reactions, utilizing the end products as energy. With the use of this bacteria we can combat plastic pollution allowing for a healthier and safer environment
The Ideonella sakaiensis bacteria was first identified in Japan at Kenji Miyamoto of Keio university via isolation from sediment samples outside a plastic bottle recycling facility.. This bacterium uses the PET molecule of plastic as its source of carbon and energy it is an aerobic, Gram negative bacteria. This rod-shaped bacterium is incapable of forming spores. The cells compose of a single flagellum that aids in motility. The colony sizes vary around 0.6-0.8 micrometers with a width of 1.2 micrometers. They grow in colonies and have thin appendages, they also have a smooth, colourless characteristic and is circular. There is a 70.4% G+C content of genomic DNA.
The oxidase and catalase test of I. sakaiensis is positive. Ideonella sakaiensis has the ability of breaking down polyethylene terephthalate (PET). PET has a chemical composition of ethylene glycol as well as Dimethylterephtalate (DMT). A discovery was made by Japanese scientists that identified the bacteriums abilities to grow and thrive on plastic whilst breaking down PET. Ideonella sakaiensis produce an enzyme called PET hydrolase (PETase) that allows for the degradation of PET into mono(2-hydroxyethyl)terephthalic acid (MHET) as well as a Terephthalic acid and ethylene glycol heterodimer.
Ester bonds are hydrolyzed by PETase, these bonds have high specificity, as a result the MHET is broken down into monomer constituents via a lipid anchored MHETase on the outer membrane of the cell.
The aromatic terephthalic acid within the cell is then oxidized via the terephthalic acid 1,2-dioxygenase as well as the 1,2 dihydroxy-3,5-cyclohexadiene-1,4 dicarboxylate dehydrogenase forming a catechol intermediate. This ring is then cleaved via PCA 3,4-dioxygenase prior to the compound being integrated in other metabolic pathways. The molecules formed are utilized as energy to build biomolecules in the cell with the carbon being mineralized and released.
Characteristics and function of Ideonella sakaiensis and the process of degradation
Ppublished: June 22 2018
Acknowledgement - Dr Jee Jap Meng
Courtesy of Taylor's University Lakeside Campus, Subang Jaya.
Thorough explanation of how Ideonella sakaiensis degrades as well as assimilates plastic. It shows how this bacterium can become a game changer to a world that being destroyed by plastic.
The massive waste of poly(ethylene terephthalate) (PET) that ends up in the landfills and oceans and needs hundreds of years for degradation has attracted global concern. The poor stability and productivity of the available PET biocatalysts hinder their industrial applications. Active PET biocatalysts can provide a promising avenue for PET bioconversion and recycling. Therefore, there is an urgent need to develop new strategies that could enhance the stability, catalytic activity, solubility, productivity, and re-usability of these PET biocatalysts under harsh conditions such as high temperatures, pH, and salinity. This has raised great attention in using bioengineering strategies to improve PET biocatalysts’ robustness and catalytic behavior. Herein, historical and forecasting data of plastic production and disposal were critically reviewed. Challenges facing the PET degradation process and available strategies that could be used to solve them were critically highlighted and summarized. In this review, we also discussed the recent progress in enzyme bioengineering approaches used for discovering new PET biocatalysts, elucidating the degradation mechanism, and improving the catalytic performance, solubility, and productivity, critically assess their strength and weakness and highlighting the gaps of the available data. Discovery of more potential PET hydrolases and studying their molecular mechanism extensively via solving their crystal structure will widen this research area to move forward the industrial application. A deeper knowledge of PET molecular and degradation mechanisms will give great insight into the future identification of related enzymes. The reported bioengineering strategies during this review could be used to reduce PET crystallinity and to increase the operational temperature of PET hydrolyzing enzymes.
The discovery of the bacteria, Ideonella sakaiensis 201-F6T, was published in the journal Science in March 2016. The brand new species was identified by microbiologists from Kyoto Institute of Technology and Keio University while they were attempting to gather samples of sediment, soil, and wastewater that had been contaminated by poly(ethylene terephthalate) (PET) near plastic bottle recycling locations in Sakai, Japan. The intriguing characteristic of this novel bacterium is its ability to eat this type of plastic that was previously considered to be one of the most infamously resistant materials (1).
Characteristics of Ideonella sakainesis explained in detail with table.
