Plastic waste is a problem but it is also opportunity to turn into raw material provides beneficial uses to society. Researchers at Rensselaer Polytechnic Institute (RPI) in the United States have developed a strain of bacteria that can convert plastic waste into plastic waste. biodegradable silk with multiple uses.
The study containing the results was published on: Microbial Cell FactoriesIt represents the first time a group of scientists managed to grow bacteria converting polyethylene plasticIt is used in many disposable products, a high value protein product.
This product, which researchers call “biology-inspired spider web”, similarity to the silk used by spiders to weave their webs, It has applications in textiles, cosmetics and even medicine.
“Spider webs are nature’s Kevlar”said Helen Zha, professor of chemical and biological engineering and one of the RPI researchers leading the project. “It could be almost as strong as steel. However, since its density is six times less than steel, it is very light. As a bioplastic, it is elastic, strong, non-toxic and biodegradable.”
All these properties make it an excellent material for a future where creating renewable resources and avoiding persistent plastic pollution will be priority goals, Zha said.
Polyethylene plastic, found in products such as plastic bags, water bottles and food packaging, is the biggest culprit in plastic pollution worldwide and It can take over 1000 years to decompose naturally.
Additionally, only a small fraction of all polyethylene plastic produced in the world is recycled, so the bacteria used in the study may help “recycle” this waste.
The bacteria used can eat polyethylene naturally, but they studied how to convert polyethylene’s carbon atoms into a genetically encoded silk protein.
Pseudomonas aeruginosaThe name of the bacteria used in the study can naturally consume polyethylene as a food source. The RPI team examined how this bacterium could ‘engineer’ the carbon atoms of polyethylene into a genetically encoded silk protein.
Surprisingly, they found that the bacteria they grew in the laboratory could produce silk protein at a yield rivaling some types of bacteria more traditionally used in biomanufacturing.
This is how plastic is recycled
In fact, the biological process underlying this innovation is something society has used for thousands of years. “Essentially, bacteria ferment plastic.. Fermentation is used to make and preserve all kinds of foods, such as cheese, bread and wine, and in the biochemical industry to produce antibiotics, amino acids and organic acids,” explained the authors of the discovery.
The plastic is first “predigested” to allow bacteria to ferment the polyethylenesaid Professor Zha. Just as humans must chew and cut our food into smaller pieces so that our bodies can use it, bacteria have a hard time eating the long chains of molecules or polymers that make up polyethylene.
Zha and Matteos Koffas, another of the authors on the study, collaborated with researchers at Argonne National Laboratory. They depolymerized the plastic by heating it under pressure, producing a soft, waxy substance.. The team then placed a layer of plastic-derived wax on the bottom of the vials, which served as a food source for bacteria to grow. This contrasts with typical fermentation, where sugars are used as a nutrient source.
“Instead of feeding the bacteria with the cake, we feed it with the candles on the cake,” Zha said.
Then, while a hot plate slowly rotates the contents of the vials, bacteria worked. After 72 hours, the scientists filtered the bacteria from the liquid culture, purified the silk protein, and freeze-dried it. At this stage, the protein, which resembles torn cotton balls, could potentially be spun or converted into other useful forms.
An innovative process
“What’s really interesting about this process is that, unlike the way plastics are produced today, Our process consumes little energy and does not require the use of toxic chemicals” added Helen Zha. “The world’s best chemists couldn’t turn polyethylene into spider silk, but these bacteria can. “We really benefit from what nature has developed for us.”
But before recycled spider silk products become a reality, researchers first They will need to find ways to produce silk protein more efficiently.
“This study reveals that we can use these bacteria to convert plastic into spider silk. We now want to investigate whether changing the bacteria or other aspects of the process allows us to increase production,” Koffas said.
Reference work: DOI: 10.1186/s12934-023-02220-0