Ideonella sakaiensis is a bacterium with a unique ability to break down polyethylene terephthalate (PET), a common type of plastic. This microorganism has garnered attention for its potential to address the global plastic pollution crisis. Its discovery offers new avenues for developing solutions for managing plastic waste and mitigating its environmental impact.
The Discovery of Ideonella sakaiensis
The bacterium Ideonella sakaiensis was identified in 2016 by a team of Japanese researchers led by Kohei Oda and Kenji Miyamoto. They found this microorganism in a sediment sample collected from a plastic bottle recycling facility in Sakai City, Japan. This location, rich in PET waste, provided the ideal environment for a plastic-degrading organism to evolve.
The scientists observed that this bacterium could use PET as its primary source of carbon and energy. Before this discovery, few bacteria or fungi were known to degrade PET, and none were definitively known to utilize it as their main food source. This ability highlighted its potential for environmental remediation.
How the Bacterium Breaks Down Plastic
Ideonella sakaiensis degrades PET plastic through a two-step enzymatic process involving two distinct enzymes: PETase and MHETase. The bacterium first adheres to the surface of the PET plastic. It then secretes PETase, which begins to break down the large PET polymer chains.
PETase works by hydrolyzing the ester bonds within the PET structure, cleaving the plastic molecules into smaller pieces. This initial breakdown yields an intermediate product called mono(2-hydroxyethyl)terephthalic acid, commonly known as MHET.
Once MHET is formed, MHETase takes over. MHETase further breaks down MHET into its two constituent monomers: terephthalic acid (TPA) and ethylene glycol (EG). These simple molecules are then readily absorbed by the bacterium. Ideonella sakaiensis uses these monomers as a food source, converting them into energy and building blocks for its growth. This enzymatic pathway allows the bacterium to deconstruct PET plastic, turning a persistent pollutant into usable nutrients.
Implications for Plastic Pollution
The discovery of Ideonella sakaiensis offers promise for addressing the global plastic pollution crisis. This bacterium’s ability to degrade PET plastics could lead to advancements in bioremediation, a process that uses biological organisms to neutralize pollutants.
The potential applications extend to more sustainable methods for plastic recycling. Traditional mechanical and chemical recycling processes often have limitations, but biological approaches could offer an alternative. The breakdown of PET into its original monomers, TPA and EG, could enable the creation of a “circular economy” for plastics. In this system, plastic waste is broken down into its fundamental components, which can then be used to create new plastics, reducing the reliance on virgin fossil resources.
While the prospects are encouraging, challenges remain before these processes can be scaled up for widespread industrial use. For example, a single Ideonella sakaiensis bacterium degrades a small amount of plastic, meaning billions would be needed for a significant impact. Research continues to focus on genetically engineering enzymes like PETase to increase their efficiency and stability, potentially allowing them to degrade higher volumes of plastic more quickly.