Creating “living plastic” that contains germs that enable it to decompose

Plastic takes tens, and sometimes hundreds of years, to decompose, causing this type of waste to pollute the land and oceans.

That's why scientists around the world are constantly working to develop technologies to break down plastic in the most efficient ways.

With this in mind, a team of scientists led by the University of California, San Diego, developed a biodegradable plastic filled with bacterial spores and thermoplastic polyurethane pellets.

The team, led by the Jacobs School of Engineering and the Materials Science and Engineering Research Center (MRSEC) at the University of San Diego, succeeded in designing a “living plastic” that can be composted.

This “living plastic,” according to the study, is a biodegradable form of thermoplastic polyurethane (TPU), a type of durable commercial plastic used to make shoes, mats (carpets), pillows, and foam.

The biodegradable material was manufactured by filling it with bacterial spores of the Bacillus subtilis strain, which have the ability to decompose plastic polymeric materials.

These bacteria, which are very widespread in the soil, have the property of germination and decomposition when they are exposed to the nutrients contained in the fertilizer at the end of their life cycle.

“It's an inherent property of these bacteria,” said John Pokorski, professor of nanoengineering and co-lead author of the study published in Nature Communications. "We took some strains and evaluated their ability to use TPU as their sole carbon source, and then selected the strain that grew better".

The researchers used an inactive type of bacteria, due to its resistance to harsh environmental conditions because it possesses a protective shield. They engineered it to be highly resilient to temperatures.

To make the new biodegradable plastic, the scientists introduced spores and thermoplastic polyurethane granules into a pressing machine, where both components were mixed and melted at a temperature of 135 degrees Celsius. Then they made plastic strips as is usually done.

The biodegradability of the resulting material was then evaluated and it was revealed that the water and other nutrients present in the compost led to the germination of spores inside the plastic, which biodegraded by 90% after 5 months in the compost, under ideal conditions of 37°C with humidity. Ranging from 44 to 55%.

Scientists also discovered another advantage of this material, which is that plastic made from Bacillus subtilis is 37% stronger and 30% less likely to break compared to traditional thermoplastic polyurethane.

In this way, the bacterial spores on the material act as a reinforcing “filler.”

The detailed study was published in the journal Nature Communications.