New Living Plastic Breaks Down After Disposal

Scientists have developed a ‘living plastic‘ that self-destructs when it starts to erode. During composting, this innovative material breaks down in just a month, whereas conventional plastics can take up to 55 days to decompose under similar conditions.

This promising technology is inspired by plastic-degrading proteins, naturally produced by a type of bacteria discovered at a recycling plant in Japan in 2016. Since then, researchers have identified other bacteria that have evolved enzymes capable of breaking down plastic.

These natural proteins have inspired synthetic versions that are even more effective at digesting plastic waste.

Incorporating Enzyme-Secreting Spores into Plastics

At the Chinese Academy of Sciences (CAS), synthetic biologist Chenwang Tang and his team have managed to incorporate bacterial spores that secrete these enzymes directly into polycaprolactone (PCL) plastic. This means that as the plastic begins to break down, the released enzymes can complete the degradation process.

Enzymes, being large and complex proteins, are typically unstable or fragile. To address this, the researchers engineered the gene for a lipase enzyme from the bacterium Burkholderia cepacia (BC) into the DNA of another microbe, Bacillus subtilis, which, in spore form, can withstand high temperatures and pressures.

Enhanced Plastic Degradation with Engineered Enzymes

As the plastic’s surface erodes, the freed spores start to germinate, leading the growing B. subtilis to express its version of BC-lipase, which effectively degrades the PCL molecules.

When another lipase from the yeast Candida antarctica was used to accelerate the process, the plastic degraded within a week. In contrast, traditional PCL plastics treated under the same conditions remained intact for over three weeks.

Testing Spore Survival in Various Plastics Production

The temperatures and pressures needed to produce PCL are not as extreme as those required for other types of plastics. To see if the spores could endure the processes needed to create other plastics, researchers at CAS modified the bacteria to express fluorescent markers.

They tested several types of plastic, including PBS (polybutylene succinate), PBAT (polybutylene adipate-co-terephthalate), PLA (polylactic acid), PHA (polyhydroxyalkanoates), and even PET (polyethylene terephthalate), which requires temperatures up to 300°C.

When these spore-infused plastics were physically degraded or boiled, they began to glow, indicating that the spores survived the ‘baking process‘ and released their contents as planned when the plastic started to erode.

Durability and Robustness of Living Plastics

The research team at CAS noted, “The living plastics remained stable when soaked in soda (Sprite) for 60 days, suggesting their potential use as packaging materials.” Additionally, the plastics were able to “completely disintegrate without the use of antibiotics, demonstrating the robustness of the system.”

While this study is only a proof of concept, it presents an intriguing potential solution to the escalating issue of plastic pollution. Over the past two decades, plastic production has doubled, and the environmental impact of plastic waste is becoming increasingly evident.

The CAS team hopes their new technique could eventually lead to the development of sustainable, biodegradable materials that do not pollute the planet for hundreds of years after a single use.

Read the original article on: Science Alert

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