ABSTRACT
Poly(3-hydroxybutyrate) [P(3HB)] was produced by Alcaligenes eutrophus from fructose or butyric acid in nitrogen-free media at differ ent pHs and temperatures, and the time-dependent changes in the molec ular weight of P(3HB) were studied. P(3HB) polymers were accumu lated within cells in the presence of a carbon source, and the rate of P(3HB) accumulation increased with temperature in the 16-35°C range but was almost independent of the pH value (5.0-8.0) of the media. The apparent activation energy for the rate of P(3HB^accumulation was 30 kJ/mol. The number-average molecular weight (M n) of P(3HB) poly mers increased rapidly with time during the course of P(3HB) accumula tion to reach a maximum value ((10 ± 2 x 105) at around 6 hours of incubation, followed by a gradual decrease in M n with time. The polydispersities (A/W/M n) of P(3HB) polymers increased from L5 to 2.0 during P(3HB) accumulation. The time-dependent changes in M n have been accounted for in terms of the kinetic model in which a chain trans fer agent is formed during the course of P(3HB) synthesis and reacts with a growing chain of P(3HB) on the active site of polymerase to regulate the length of P(3HB) chain.
