EFFECTS OF HIGHER-ORDER STRUCTURE OF POLY(3-HYDROXYBUTYRATE) ON ITS BIODEGRADATION .1. EFFECTS OF HEAT-TREATMENT ON MICROBIAL-DEGRADATION

To clarify how the biodegradation of plastic is affected by physical properties based on the plastic's higher-order structure, the microbial degradability of heat-treated poly(3-hydroxybutyrate) (PHB) samples was studied. Cast-film samples and fibrous samples prepared with heat treatment were degraded by an isolated degrading bacterium: strain SC-17. Consequently, it was found that the higher-order structure properties such as crystallinity and modulus of elasticity of PHB acted as suppression factors. SEM observations of the degraded PHB films showed unique degradation patterns such as spherical and tubular holes on the surfaces and cells of SC-17 in process of degrading the PHB surface. These patterns are thought to result from colonization of SC-17 on the surfaces. From the results, it was suggested that the surface of the PHB was important as a growing field for the degrading bacterium and that the higher-order structure properties of the PHB affected not only the degradation reaction but also the colonization of the degrading bacterium on the surface.