Polyester is one of the most widely used synthetic materials in the world, but it is also one of the most persistent and difficult to recycle.
It is a type of plastic that is made from petroleum and consists of long chains of molecules called polyesters, and is used for various purposes, such as clothing, packaging, furniture, and carpets.
However, when polyester products are discarded, they end up in landfills or oceans, where they can take hundreds of years to decompose and harm the environment and wildlife.
To address this problem, scientists are looking for ways to break down polyester using biological methods, such as bacteria or enzymes.
Bacteria are microscopic organisms that can feed on different substances and produce enzymes that can catalyze chemical reactions.
Enzymes are proteins that can speed up the breakdown of molecules by cutting them into smaller pieces.
Some bacteria and enzymes have been found to have the ability to degrade polyester, but they are often inefficient or limited in their activity.
However, a recent study has discovered a new bacterium that has three enzymes that may be able to break down polyester more effectively.
The study was conducted by researchers from Brunel University London and published in the journal Environmental Microbiology.
How the bacterium was isolated from waste plastic
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The researchers collected waste plastic from a beach in Ireland, where they found expanded polystyrene (EPS), a type of foam-like polyester that is used for insulation and packaging.
They noticed that the EPS had colonies of bacteria growing on it, which suggested that the bacteria could be using the plastic as a source of carbon and energy.
The researchers then conducted an experiment to enrich and isolate the bacteria that had the highest plastic-degrading activity.
They cut the EPS into small pieces and added them to two different types of media: one with nutrients and one without, then incubated the media for 53 days and then tested the plastic-degrading activity of the bacteria by measuring the weight loss of the EPS and the formation of holes on its surface.
According to the study, the bacteria in the nutrient-free media had higher plastic-degrading activity than those in the nutrient-rich media.
This indicated that the bacteria in the nutrient-free media had adapted to use the EPS as their sole carbon source and had developed enzymes that could break down the polyester.
The researchers then used DNA sequencing to identify the bacteria in the nutrient-free media. They found that they belonged to a species called Pseudomonas stutzeri, which is a common soil bacterium that can degrade various organic compounds.
How the bacterium's enzymes may break down polyester
The researchers further analyzed the genome of Pseudomonas stutzeri and found that it had three genes that encoded enzymes that could be involved in polyester degradation.
The enzymes are called PETase, MHETase, and Cutinase.
PETase is an enzyme that can break down polyethylene terephthalate (PET), another type of polyester that is used for making bottles and fabrics. It can cut PET into smaller molecules called mono(2-hydroxyethyl) terephthalic acid (MHET) and ethylene glycol.
MHETase is an enzyme that can break down MHET into terephthalic acid (TPA) and ethylene glycol. TPA and ethylene glycol are the building blocks of PET, so breaking them down further would prevent them from being re-polymerized into new plastic.
Cutinase is an enzyme that can break down cutin, a natural polyester that is found in plant cell walls. It can cut cutin into smaller molecules called hydroxy fatty acids.
The researchers hypothesized that these three enzymes could work together to degrade EPS and other types of polyesters by cutting them into smaller molecules that could be metabolized by the bacterium or other microorganisms.
