Application and Limitation and Communication and Collaboration of a newly discovered mutant enzyme that recycles plastic in hours
Topic 1- Application and Limitation/ Communication and Collaboration of a newly discovered mutant enzyme that recycles plastic in hours
An engineered enzyme could make it easier to recycle plastic bottles and eliminate them from landfills. ERMINGUT/ISTOCKPHOTO
‘A huge step forward.’ Mutant enzyme could vastly improve recycling of plastic bottles
By Robert F. Service Apr. 8, 2020 , 5:45 PM
Recycling isn’t as guilt-free as it seems. Only about 30% of the plastic that goes into soda bottles gets turned into new plastic, and it often ends up as a lower strength version. Now, researchers report they’ve engineered an enzyme that can convert 90% of that same plastic back to its pristine starting materials. Work is underway to scale up the technology and open a demonstration plant next year. Application and Limitation
“This is a huge step forward,” says John McGeehan, who directs the center for enzyme innovation at the University of Portsmouth and who was not involved with the work.
Polyethylene terephthalate (PET) is one of the world’s most commonly used plastics, with some 70 million tons produced annually. PET bottles are already recycled in many places. But the current approach has problems. For starters, recycling companies typically end up with a broad mix of different colors of the plastic. They then use high temperatures to melt those down, producing a gray or black plastic starting material that few companies want to use to package their products.
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Instead, the material is typically turned into carpets or other low-grade plastic fibers that eventually end up in a landfill or get incinerated. “It’s not really recycling at all,” McGeehan says.
To get around this concern, scientists have searched for enzymes in microbes that break down PET and other plastics. In 2012, researchers at Osaka University found one such enzyme in a compost heap. That enzyme, known as leaf-branch compost cutinase (LLC), snips the bonds between PET’s two building blocks: terephthalate and ethylene glycol. But LLC, which evolved to break down the waxy protective coating on many plants’ leaves, slowly breaks apart PET bonds only, and falls apart after just a few days of working at 65°C, the temperature at which PET begins to soften, which allows the enzyme to more easily wiggle into the polymer to reach the links it seeks to break.
To re-engineer LLC, Alain Marty, the chief scientific officer at Carbios, a sustainable plastics company, teamed up with Isabelle Andre, an enzyme engineering expert at the University of Toulouse. Communication and Collaboration They started by analyzing the crystal structure of the enzyme, identifying key amino acids at the site where the enzyme binds to the chemical linkers between PET’s terephthalate and ethylene glycol groups. They also looked for ways to make the enzyme work at higher temperatures.
The researchers then generated hundreds of mutant enzymes changing amino acids at the binding site and adding in heat-stabilizing ones. They then mass produced the mutants in bacteria and screened them to find efficient PET breakers. After repeating this process for several rounds, they isolated a mutant enzyme that’s 10,000 times more efficient at PET bond breaking than the native LLC. It also works without breaking down at 72°C, close to the temperature at which PET becomes molten.
In a small reactor designed to test the enzyme, the team found that it could break down 90% of 200 grams of PET in 10 hours. The researchers then used the terephthalate and ethylene glycol building blocks generated by the enzyme to generate new PET and produce plastic bottles that were just as strong as those made from conventional plastics, they report today in Nature.
“This is very exciting,” McGeehan says. “It shows this is really viable.”
Whether it will be economically viable remains unclear, however. McGeehan notes that one main advantage is that the enzyme has no difficulty in making pure PET building blocks from a mix of plastics containing ones other than PET, even PET bottles of different colors. That’s because the engineered enzyme only breaks bonds linking the two PET components, returning them to their original form, while ignoring dyes and other plastics in the mix. As a result, he says, companies and consumers may be willing to pay a bit more for a recycled plastic that is as durable and attractive as the virgin material.
Marty says that Carbios is building a demonstration plant that is expected to recycle hundreds of tons of PET per year. The enzyme can’t recycle other major types of plastics, such as polyethylene and polystyrene, which have bonds between building blocks that are harder to break. But if successful, it could make it help society deal with one of the most challenging plastic problems we face.
Posted in: Chemistry
doi:10.1126/science.abc1556
A mutant bacterial enzyme can break down plastic for recycling in just hours
Published: April 9, 2020 at 9:09 a.m. ET
By
Rachel Koning Beals
Developer Carbios says Pepsi and L’Oréal are on board
GETTY IMAGES
Use of a mutant bacterial enzyme that breaks down plastic bottles for recycling in mere hours is finding traction.
The French company behind the breakthrough, Carbios, said the enzyme was originally discovered in 2012 in leaf compost. It’s now been found in the lab to reduce bottles to chemical building blocks that can be used to make food-grade plastic strong enough for new bottles. The research team used the optimized enzyme to break down a metric ton of plastic bottles, which were 90% degraded within 10 hours. Existing recycling technologies historically could only turn old plastic into a fiber substitute for clothing and carpets.
The advancement for the enzyme was revealed in research published on Wednesday in the journal Nature. Carbios’s own scientist, along with academic support from the Toulouse Biotechnology Institute, were behind the study. But the journal publication could bring more attention from industry heavyweights. Communication and Collaboration
Carbios ALCRB, +4.67% has said it was aiming for industrial-scale recycling within five years. It has partnered with Pepsi PEP, +0.37% , L’Oréal and others to accelerate development. The company earlier this year announced a deal with the biotechnology company Novozymes NVZMY, +1.05% to produce the new enzyme at scale using fungi.
There are some limitations. Application and Limitation Waste bottles must be ground up and heated before the enzyme is added, so the recycled polyethylene terephthalate, or PET, will be more expensive than virgin plastic. But the company explained to the Guardian that existing lower-quality recycled plastic sells at a premium due to a shortage of supply, which narrows the pricing gap.
Carbios said reduction in plastic use goes part of the way toward lessening the environmental impact from landfills and ocean pollution. But, it says, the value of plastics in food packaging, medical care and transportation can’t be ignored, which is why it pushes for a circular economy favoring converting plastic waste.
Most of the 350 million-plus metric tons of plastic produced every year enter the world’s terrestrial and marine environments. And some estimates suggest that plastic costs humanity over US$2.2 trillion a year in environmental and social damage, an academic paper in the journal Frontiers in Marine Science said.
Earlier this year, German researchers reported the discovery of a bug that feasts on toxic polyurethane and earlier work had shown that a wax moth larvae, usually used as fish bait, can degrade polythene bags.
Communication and Collaboration
- Science is a global enterprise that relies on clear communication, international conventions, and review and verification of results.
- Collaboration between scientists, governments, and other agencies is often required in scientific research and enterprise.
Application and Limitation
- Scientific knowledge, understanding, and inquiry can enable scientists to develop solutions, make discoveries, design action for sustainability, evaluate economic, social, cultural, and environmental impacts, offer valid explanations, and make reliable predictions.
- The use of scientific knowledge may have beneficial or unexpected consequences; this requires monitoring, assessment, and evaluation of risk, and provides opportunities for innovation.
- Science informs public debate and is in turn influenced by public debate; at times, there may be complex, unanticipated variables or insufficient data that may limit possible conclusions.
Topic 1 DNA and Protein (Enzymes)
| Proteins are essential to cell structure and function.
Examples of proteins with specific shapes include enzymes, some hormones, receptor proteins, and antibodies. · Explain why the three-dimensional shape of a protein is critical to its function. Enzymes are specific for their substrate and increase reaction rates by lowering activation energy. · Describe the induced-fit model of enzyme–substrate binding.
Enzymes have specific functions and are affected by factors including: – temperature – pH – presence of inhibitors. The rate of an enzyme-controlled reaction is affected by: – concentrations of reactants – concentration of the enzyme. |
Discuss examples of proteins whose three-dimensional structure can facilitate the recognition and binding of specific molecules, including enzymes and substrates, and cell membrane receptors and hormones.
Use examples to emphasise enzyme specificity and reinforce the importance of the three-dimensional shape of proteins. |
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| Investigate the effect that conditions such as temperature, pH, substrate concentration, product concentration, and chemical inhibitors can have on enzyme activity. | ||
| Research ways in which an understanding of enzyme inhibitors enables scientists to develop solutions to health and environmental problems. Identify beneficial outcomes or unexpected consequences.
Examples include: · pesticides (e.g. glyphosate) · drugs (e.g. ritonavir) · some types of chemotherapy. Investigate how knowledge of the specificity of antibodies enables the development of medical procedures and diagnostic tools. Examples include blood transfusions and the ELISA assay. |
