Research & Development

Plastic-eating bacteria help the environment

Plastic pollution has become a serious environmental concern in recent years as a result of the fast manufacture of Polyethylene Terephthalate (PET), a single-use plastic. It is prevalent in Asian and African countries due to ineffective garbage pickup methods. Plastic trash has become a huge issue for marine and terrestrial ecosystems as a result of the widespread manufacture of plastic in the form of food containers, bottles, fibers, films, and so on. Plastic is a polymeric substance composed of huge, long chains of molecules joined by a series of links. Polyethylene Terephthalate is a polyester-family thermoplastic polymer. PET is utilized as a fiber in the fabric manufacturing industry, as a food container for different liquid items, and as glass fiber in the resin manufacturing industry. Because single-use plastics decay mostly through a process known as photodegradation, which is a lengthy process, there is a need to create alternatives for single-use plastic deterioration.

A heterotrophic bacteria called Ideonella sakaiensis may degrade Polyethylene Terephthalate (PET). A motile organelle connected to the bacteria is called a flagellum. To adhere to the plastic surfaces, the flagellum is utilized. The PET-degrading enzymes, known as PETases are released onto the PET surfaces. These PETase enzymes found in Ideonella sakaiensis are believed to have the highest PET hydrolytic activity when compared to the PETase enzyme of other bacteria, eg. Thermobifida fusca. The PETase enzyme degrades polyethylene terephthalate (PET) into mono (2-hydroxyethyl) terephthalic acid (MHET), a heterodimer comprised of terephthalic acid (TPA) and ethylene glycol (EG). The MHET is subsequently transformed into two monomeric units by the MHET hydrolase enzyme (MHETase), which is found on the bacterial cell's outer membrane. PET also degrades into Bis - (2-hydroxyethyl) terephthalate as an intermediary (BHET). After PET hydrolysis, this BHET may be transformed into MHET. Ethylene glycol is then used up by I.sakaiensis and other bacteria. Terephthalic acid is then imported into the I.sakaiensis cell through terephthalic acid transporting protein. After reaching the bacterial cell, the terephthalic acid molecule is then oxidized into a catechol intermediate. The catechol ring is cleaved by PCA 3,4-dioxygenase before it integrates into other pathways such as the TCA cycle. Both the molecules generated from the degradation of PET, are used by the bacterial cell to produce energy. Eventually, the carbon is mineralized to carbon dioxide which is released into the environment
(Source: https://www.nationalgeographic.com/environment/article/plastic-pollution)

Dr. Md. Monirul Islam
Senior Scientist
ASRBC, ACI Seed