Polyhydroxyalkanoates are linear polyesters generated by fermentation of sugars or lipids. They are generally made and used by bacteria to store energy and commercially to make bioplastics. Formation of polyhydroxyalkanoates from hydroxy fatty acids of short (3–5 carbons) or medium (6–14 carbons) chain length is catalysed by the polyhydroxyalkanoate (PHA) synthase enzymes.