Plastic-eating enzyme 'cocktail' heralds new hope for plastic waste

September 28, 2020

EMBARGOED: 20:00 BST (15:00 U.S. Eastern time), 28 September 2020

(images and video available via Dropbox - link at end)

Plastic-eating enzyme 'cocktail' heralds new hope for plastic waste

The scientists who re-engineered the plastic-eating enzyme PETase have now created an enzyme 'cocktail' which can digest plastic up to six times faster.

A second enzyme, found in the same rubbish dwelling bacterium that lives on a diet of plastic bottles, has been combined with PETase to speed up the breakdown of plastic.

PETase breaks down polyethylene terephthalate (PET) back into its building blocks, creating an opportunity to recycle plastic infinitely and reduce plastic pollution and the greenhouse gases driving climate change.

PET is the most common thermoplastic, used to make single-use drinks bottles, clothing and carpets and it takes hundreds of years to break down in the environment, but PETase can shorten this time to days.

The initial discovery set up the prospect of a revolution in plastic recycling, creating a potential low-energy solution to tackle plastic waste. The team engineered the natural PETase enzyme in the laboratory to be around 20 percent faster at breaking down PET.

Now, the same trans-Atlantic team have combined PETase and its 'partner', a second enzyme called MHETase, to generate much bigger improvements: simply mixing PETase with MHETase doubled the speed of PET breakdown, and engineering a connection between the two enzymes to create a 'super-enzyme', increased this activity by a further three times.

The study is published in the journal Proceedings of the National Academy of Sciences of the United States of America.

The team was co-led by the scientists who engineered PETase, Professor John McGeehan, Director of the Centre for Enzyme Innovation (CEI) at the University of Portsmouth, and Dr Gregg Beckham, Senior Research Fellow at the National Renewable Energy Laboratory (NREL) in the US.

Professor McGeehan said: "Gregg and I were chatting about how PETase attacks the surface of the plastics and MHETase chops things up further, so it seemed natural to see if we could use them together, mimicking what happens in nature.

"Our first experiments showed that they did indeed work better together, so we decided to try to physically link them, like two Pac-men joined by a piece of string.

"It took a great deal of work on both sides of the Atlantic, but it was worth the effort - we were delighted to see that our new chimeric enzyme is up to three times faster than the naturally evolved separate enzymes, opening new avenues for further improvements."

The original PETase enzyme discovery heralded the first hope that a solution to the global plastic pollution problem might be within grasp, though PETase alone is not yet fast enough to make the process commercially viable to handle the tons of discarded PET bottles littering the planet.

Combining it with a second enzyme, and finding together they work even faster, means another leap forward has been taken towards finding a solution to plastic waste.

PETase and the new combined MHETase-PETase both work by digesting PET plastic, returning it to its original building blocks. This allows for plastics to be made and reused endlessly, reducing our reliance on fossil resources such as oil and gas.

Professor McGeehan used the Diamond Light Source, in Oxfordshire, a synchrotron that uses intense beams of X-rays 10 billion times brighter than the Sun to act as a microscope powerful enough to see individual atoms. This allowed the team to solve the 3D structure of the MHETase enzyme, giving them the molecular blueprints to begin engineering a faster enzyme system.

The new research combined structural, computational, biochemical and bioinformatics approaches to reveal molecular insights into its structure and how it functions. The study was a huge team effort involving scientists at all levels of their careers.

One of the most junior authors, Rosie Graham, a joint Portsmouth CEI-NREL PhD student said: "My favourite part of research is how the ideas start, whether it's over coffee, on a train commute or when passing in the university corridors it can really be at any moment.

"It's a really great opportunity to learn and grow as part of this UK-USA collaboration and even more so to contribute another piece of the story on using enzymes to tackle some of our most polluting plastics."

The Centre for Enzyme Innovation takes enzymes from the natural environment and, using synthetic biology, adapts them to create new enzymes for industry.
-end-
Article #20-06753: "Characterization and engineering of a two-enzyme system for plastics depolymerization," by Brandon C. Knott et al.

MEDIA CONTACTS:

Co-lead author Professor John E. McGeehan, University of Portsmouth
E: john.mcgeehan@port.ac.uk
Senior media and communications officer Kate Daniell, University of Portsmouth
T: 07827012498, E: kate.daniell@port.ac.uk

IMAGES/VIDEO in DROPBOX:

https://www.dropbox.com/sh/4wtxs8g9qrfbwoy/AACjJY91p23FjNrmPzg4zBtia?dl=0

University of Portsmouth

Related Enzymes Articles from Brightsurf:

Bacilli and their enzymes show prospects for several applications
This publication is devoted to the des­cription of different microbial enzymes with prospects for practical application.

Ancient enzymes can contribute to greener chemistry
A research team at Uppsala University has resurrected several billion-year-old enzymes and reprogrammed them to catalyse completely different chemical reactions than their modern versions can manage.

Advances in the production of minor ginsenosides using microorganisms and their enzymes
Advances in the Production of Minor Ginsenosides Using Microorganisms and Their Enzymes - BIO Integration https://bio-integration.org/wp-content/uploads/2020/05/bioi20200007.pdf Announcing a new article publication for BIO Integration journal.

Cold-adapted enzymes can transform at room temperature
Enzymes from cold-loving organisms that live at low temperatures, close to the freezing point of water, display highly distinctive properties.

How enzymes build sugar trees
Researchers have used cryo-electron microscopy to elucidate for the first time the structure and function of a very small enzyme embedded in cell membranes.

Energized by enzymes -- nature's catalysts
Scientists at Pacific Northwest National Laboratory are using a custom virtual reality app to design an artificial enzyme that converts carbon dioxide to formate, a kind of fuel.

Mathematical model reveals behavior of cellular enzymes
Mathematical modeling helps researchers to understand how enzymes in the body work to ensure normal functioning.

While promoting diseases like cancer, these enzymes also cannibalize each other
In diseases like cancer, atherosclerosis, and sickle cell anemia, cathepsins promote their propagation.

Researchers finally grasp the work week of enzymes
Scientists have found a novel way of monitoring individual enzymes as they chomp through fat.

How oxygen destroys the core of important enzymes
Certain enzymes, such as hydrogen-producing hydrogenases, are unstable in the presence of oxygen.

Read More: Enzymes News and Enzymes Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.