Besides the typical polymeric properties described above, an important characteristic of PHAs is their biodegradability. In nature, a vast consortium of microorganisms is able to degrade PHAs by using secreted PHA hydrolases and PHA depolymerases (for a review of the microbiology and molecular genetics of PHA degradation, see reference111). The activities of these enzymes may vary and depend on the composition of the polymer, its physical form (amorphous
or crystalline), the dimensions of the sample, and, importantly, the environmental conditions. The degradation rate of a piece
of P(3HB) is typically on the order of a few months (in anaerobic sewage [Fig. 2]) to years (in seawater) (111, 167–169).