A team of Japanese researchers has identified a bacterium species capable of breaking down plastic — polyethylene terephthalate (PET).
The bacterium uses two enzymes in sequence to break down the highly biodegradation-resistant polymer PET – in the journal Science .
Except for rare instances of two fungi that have been found to grow on a mineral medium of PET yarns, there are no reports any bacteria biologically degrading PET or growing on the chemically inert substance.
250 contaminated samples from a PET bottle recycling site were collected and microorganisms that relied on PET film as a primary source of carbon for growth were looked.
At first a distinct microbial consortium that contained a mixture of bacteria species that degraded the PET film surface at 30 degree C; 75 per cent of the PET film surface was broken down into carbon dioxide at 28 degree C were identified.
From the microbial consortium, the researchers isolated a unique bacterium — Ideonella sakaiensis 201-F6 — that could almost completely degrade a thin film of PET in a short span of six weeks at 30 degree C.
The bacterium degrades PET using two enzymes that act on it in sequence.
- First, the bacterium adheres to PET and produces an intermediate substance through hydrolysis.
- The second enzyme then works with water and acts on this intermediate substance to produce the two monomers — ethylene glycol and terephthalic acid — used for making PET through polymerisation.
- PET has been littering the environment for the last 70 years and, in 2013, 56 million tonnes of PET were produced worldwide.
- Since PET came into being only 70 years ago, a pertinent question is how this distinct bacterium evolved or naturally selected in the environment.
- Also, is not clear about the natural processes of the two unique enzymes that are capable of breaking down PET in sequential steps to evolve.