Decomposition of living plastics with destructive spores

According to the Anna Science and Technology news agency, citing New Atlas, when survival becomes difficult for certain bacteria, they turn into spores that can withstand the harshest environments. Scientists have now used this fact to produce “living plastic” that biodegrades – but only under certain conditions.

Spore is the dormant form of some types of bacteria. When the bacterium lacks nutrients, it turns into a spore. They are protected by a tough outer covering that allows them to survive high temperatures, high pressures, dryness, and caustic chemicals. This makes spores one of the most resistant forms of life. Spores can remain dormant for years or even centuries, becoming active only when stimulated by appropriate environmental cues.

Some bacteria are also known to break down plastic waste and prevent it from persisting in the environment.

Scientists from the Chinese Academy of Sciences have now taken spores of such bacteria and placed them in solid plastic, which remains hard and intact until the spores are revived.

The researchers, led by Professor Zhuojun Dai, created a form of Bacillus subtilis bacteria that was genetically engineered to secrete a plastic-degrading enzyme called BC lipase.

These microbes turn into spores when exposed to heavy metal ions. Those spores were then mixed with PCL (polycaprolactone) plastic beads, melted and molded to form solid plastic pieces.

Tests have shown that the resulting “living plastic” performs as well as conventional PCL during daily use. However, when a special enzyme is applied to the surface of the plastic, it erodes the surface of the material and revives the spores trapped inside. The revived bacteria began secreting BC lipase again and completely degraded the plastic within six to seven days.

Spores can also be regenerated by composting plastic. Samples of these materials that were placed in the soil were completely destroyed within 25 to 30 days.

It's important to note that even regular PCL will biodegrade over time, albeit over a longer period of time. In fact, the scientists were able to integrate the spores into non-biodegradable plastics such as polyethylene, then grind the plastic back to secrete BC lipase.

Further research is needed to determine the extent to which these versions of living plastic are degraded by the enzyme. It's worth noting that researchers at the University of San Diego previously created a spore-laden TPU (thermoplastic polyurethane) that, unlike conventional TPU, degrades when dumped in a landfill.

The results of this research have been published in Nature Chemical Biology.