Researchers at Virginia Tech and the University of Tennessee have characterized a polyethylene-like polyester that cellophane bees use to line their nests and that degrades in soil within months, according to a paper in the Proceedings of the National Academy of Sciences (PNAS) and a Virginia Tech release.A polyethylene-like polyester is a plastic with a crystal structure similar to polyethylene, the material in milk jugs and single-use food containers, but with ester bonds (chemical links that water and enzymes can attack) in its chains. Polyethylene can persist for centuries, the Tennessee release said, and most polyesters built to imitate it break down poorly, said University of Tennessee ecologist Laura Russo.The bee’s version is different. In soil, its polyester fell from about 73% to about 40% of the nest lining’s weight in four months, Virginia Tech said. “This is a polyester that mimics polyethylene,” said lead author Jonathan Coote, an assistant professor of sustainable biomaterials at Virginia Tech.Nest linings in soilThe cellophane bee, Colletes inaequalis, is a solitary, ground-dwelling species that does not form hives. It lines its nest cells with the polyester. In the team’s PNAS paper, published Nov. 2, the researchers characterize linings collected at two Tennessee sites in 2023, 2024 and 2026, according to a Tennessee release. Chris Ellison and Frank Bates are co-authors, Virginia Tech said.Both universities describe the material as semicrystalline, meaning it has ordered crystal regions alongside disordered ones, with a degradation temperature and crystal structure like polyethylene’s. Virginia Tech said the bee polyester likely contains cross-links, chemical bonds between neighboring chains that usually make plastics harder to break down. Coote said conventional wisdom holds such features make breakdown harder, and that the bee’s material does not follow it.Polyethylene makes up roughly one-third of world plastic production, about 160 million tons a year, the researchers said in the Virginia Tech release. Many plastics sold as biodegradable break down slowly or only under industrial conditions, the release added.What is still unprovenVirginia Tech said researchers are still working out the chemical structure that lets the bee polyester break down so fast. The team suspects an esterase enzyme, a protein that cuts ester bonds, helps cleave the chains. Separate work at the University of Konstanz found esterase enzymes in forest soil samples where a different polyester bioplastic broke down.The four-month figure is a share of lining weight, so the releases do not show how much total material was lost. The Tennessee release mentions both four months and one year of degradation without saying how they relate. Neither university says how many samples were tested or what the soil was like.Nothing in the releases shows that a manufactured version would match polyethylene’s strength or reach commercial scale. The releases name no funder and say nothing about patents or conflicts of interest.The team’s next step, Virginia Tech said, is to understand the chemistry well enough to reproduce the useful features in a manufactured material.