STRUCTURAL STUDY OF ISOLATED POLY(BETA-HYDROXYBUTYRATE) GRANULES

Nascent poly(beta-hydroxybutyrate) (PHB) granules are found in most bacterial strains and can be isolated as a milky suspension. Their structure was examined by transmission and scanning electron microscopy and has been shown to be made of two distinct components: a solid shell composed of overlapping lamellar crystals and a soft non-crystalline core. It was possible to obtain a ductile deformation of the core in liquid nitrogen even though the glass transition of isotactic PHB approaches 0-degrees-C. Finally, glycerol triacetate, a minor component of the granule, was found to be a good solvent for PHB from which metastable solutions can be obtained. Self-seeding of these solutions led to the formation of lamellar crystals comparable to the structure of the shells.