Production and characterization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) synthesized by Ralstonia eutropha in fed-batch cultures

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-6hydroxybutyrate) [P(3HB-co- 3HV-co-4HB)] terpolymers were produced in fed-batch cultures of Ralstonia e utropha (reclassified from Alcaligenes eutrophus) using glucose, propionic acid and either 4-hydroxybutyric acid or gamma-butyrolactone as carbon sour ces. The thermal and mechanical properties of terpolymers containing differ ent proportions of the constituent monomers were characterized. Most of the terpolymers possessed low melting temperatures and the majority possessed crystallization half-times between 4 and 16 min, compared with 0.5 min for poly(3-hydroxybutyrate) [P(3HB)]. For certain polymer compositions, contain ing approximately 10 mol% of both 3-hydroxyvalerate (3HV) and 4-hydroxybuty rate (4HB), the mechanical properties were superior to those of P(3HB-co-0- 30% 3HV) range of polymers and did not display any signs of deterioration o ver a one month test period. A compression molded polymer film containing 7 8 mol% 3HB, 11 mol% 3HV and 11 mol% 4HB was found to possess an elongation to break of 700% after one month, compared with 740% after molding, but ult imately declined to 35% after 13 months. The aging process was found to dep end upon the primary crystallization rate. (C) 2000 Elsevier Science Ltd. A ll rights reserved.