FIG. 1.

Chemical structure of PHAs. PHAs are generally composed of (R)-β-hydroxy fatty acids, where the pendant group (R) varies from methyl (C₁) to tridecyl (C₁₃). Other fatty acids that have been incorporated have the hydroxy group at the γ, δ, or ɛ position, while the pendant group may be saturated or unsaturated or contain substituents. The best-known PHAs are P(3HB) (R = methyl), P(3HB-3HV) (R = methyl or ethyl), and P(3HO-3HH) (R = pentyl or propyl).