Finding an economical way to make a polyester commonly found in many types of bacteria into a plastic with uses ranging from packaging to biomedical devices is a long-held scientific goal. Such a polymer would be a “green” plastic, in that it would be biodegradable. Geoffrey Coates, a professor of chemistry and chemical biology at Cornell University, Ithaca, N.Y., has partially achieved this goal by discovering a highly efficient chemical route for the synthesis of the polymer, known as poly(beta-hydroxybutyrate) or PHB. The thermoplastic polyester is widely found in nature, particularly in some bacteria, where it is formed as intracellular deposits and used as a storage form of carbon and energy. And yet it shares many of the physical and mechanical properties of petroleum-based polypropylene, with the added benefit of being biodegradable.