Plastic is one of the most useful materials in our modern world, but unfortunately it’s also one of the worst in a sustainability sense. Now, scientists at Berkeley Lab have developed a way to engineer bacteria to produce raw materials that can be made into plastics that are completely recyclable.

Plastic recycling programs mean well, but the disappointing truth is that the vast majority is incinerated or ends up in landfill. In 2019, Berkeley Lab unveiled a new type of plastic called polydiketoenamine (PDK), in which the bonds between the molecules can be broken down more easily on demand, ready to be made into something new with no loss of quality.

In previous studies, the scientists initially made PDK out of the same petrochemicals that go into regular plastic, but for the new study they’ve successfully switched to a renewable source instead. The team engineered E. coli so that it could convert sugars from plants into a molecule called triacetic acid lactone (TAL), which can then be combined with other chemicals to produce PDK.

The end result is a plastic material that can be selectively tuned to be flexible, tough or even adhesive, depending on the application at hand. Not only is this new PDK more sustainable, but the team found that it can also handle hotter working temperatures than the earlier version – up to 60 °C (140 °F). This opens up a wider range of potential applications.

In its current form, the PDK is made up of around 80% bio-content, but the team says that future versions will shoot for 100%. Other improvements that will be the focus of more work include finding ways to get bacteria to convert a wider range of plant sugars and compounds into the raw materials, and speeding up that conversion.

“Our new results are extremely encouraging,” said Corinne Scown, an author of the study. “We found that with even modest improvements to the production process, we could soon be making bio-based PDK plastics that are both cheaper and emit less CO2 than those made with fossil fuels.”

The research was published in the journal Nature Sustainability.