Morphology and crystallization behavior of nascent poly(3-hydroxybutyrate) granule

The structure of poly(3-hydroxybutyrate) (PHB) granules was examined by transmission and scanning electron microscopy (TEM and SEM). They are made of two distinct components: a solid shell (overlapping lamellar crystals) and a non-crystalline core.;TEM examination of sections of PHB granules revealed that, upon annealing, the core molecules transform into stacks of lamellar crystals of $sim$50-70A in thickness. Fourier transform infrared results revealed the presence of bound water in a sample of freeze dried granules. Solid state $sp{13}$C NMR results showed that the mobility of the granule core molecules was partly retained upon drying. A model for biosynthesis where emerging PHB chains in an extended conformation are simultaneously hydrogen bonded to water molecules is proposed.;Hydrolytic degradation of PHB granules in hot HCl proceeds through random scission of the molecules of both the crystalline shell and the non-crystalline core indiscriminately.