An “energy storage” substance that is naturally produced by certain bacteria, yeasts, and plants. When removed from the bacteria and purified, this substance has physical properties quite similar to thermoplastics like polystyrene. PHB can quickly be broken down by soil microorganisms, so PHB is a biodegradable plastic. Three separate enzymes are utilized by the organism in order to make the PHB molecule. In 1994, researchers succeeded in transferring genes for PHB production into the weed plant Arabidopsis thaliana and the crop plant rapeseed (canola).