Nature has a biodegradable plastic. Science wants to reverse engineer it

Cellophane bees, which nest in soil, coat their egg chambers with a thin film made from silk and a polyethylene-like polyester. The lining protects developing larvae from moisture and microbes, yet disappears from the soil rather than accumulating around long-used nesting sites. In a study of Colletes inaequalis nests in Tennessee, researchers analyzed fresh material and linings recovered after four, seven, and eleven months. Fresh lining was about 73 percent polyester and 27 percent silk. The polyester was semicrystalline and likely cross-linked - a structure usually associated with durable plastics that are difficult to break down.

The material’s condition changed in step with the bee’s development. After four months, polyester made up only 40 percent of the lining, though it still remained flexible and protective. By seven months it cracked easily, and by eleven it crumbled. Researchers say this rapid soil degradation, especially for a cross-linked material, could offer clues for designing plastics that perform like conventional packaging but do not persist in the environment. They suspect the polyester’s crystal structure may expose degradable bonds, and that an enzyme in the lining, possibly from the bee, may help break them. The next step is to identify the mechanisms and reproduce them in materials that can be manufactured at useful scale.