The properties of PHAs can be tuned by varying the HV content, its increase t exult mg in an increase in the impact strength and a decrease in melting temperature und glass transition, tensile strength, crystallinity and water vapotit pcnnettbiliiy (40-42). Regarding the mechanical properties of P3HB-CO-3HV copolytnets, studies suggest that the 3HB and 3HV units are isodimorphous because of their similarity in shape and size and that the 3HV units arc incorporated into the P(3I IB) crystal lattice (4 3,44|. As a result, the properties of P(3HB-co-3HV) arc not significantly improved in compat ison with the P(3HB) homopolymer. However,copolymers with improved mechanical properties can be prepared via copolymcrization of 31 IB with longer chain hydro-xyalkanoic acids, which form a separate crystalline lattice or do not crystallize at all, such as is the case for copolymers of 3HB and 3-hydroxyhcxanoate