Burkholderia sp, was grown on sucrose-containing mineral salts medium with phosphate limitation to induce poly(hydroxyalkanoate) (PHA) accumulation. Under these conditions the cultures accumulated 3-hydroxybutyric acid (3HB) and 3-hydroxy-4-pentenoic acid (3HPE) containing polyesters. Solvent fractionation of the purified polyester indicated the presence of two homopolymers, poly(3HB) and poly(3HPE), rather than a co-polyester with random monomer distribution as has been reported previously [Rodrigues, M. F. A.; da Silva, L. F.; Gomez, G. C.; Valentin, H. E.; Steinbuchel, A. Appl. Microbiol. Biotechnol. 1995, 43, 880]. The simultaneous accumulation of two homopolyesters by Burkholderia sp. was confirmed by NMR spectroscopic analysis. Therefore, this is the first report on accumulation of a poly(3HPE) homopolyester and its accumulation from structurally unrelated carbon sources. Purified poly(3HPE) was cross-linked by UV radiation and subjected to epoxidation using 3-chloroperoxybenzoic acid. Introduction of epoxides into the 3HPE homopolyester was found to increase the glass transition temperature.