Influence of the morphology and of the supermolecular structure on the enzymatic degradation of bacterial poly(3-hydroxybutyrate)

Films of poly(3-hydroxybutyrate) (PHB) were crystallized from the melt by d ifferent thermal treatments and submitted to enzymatic degradation by using a PHB depolymerase purified from Aureobacterium saperdae culture. The morp hology and the supermolecular structure of PHB films were investigated to e xplain differences in the kinetics of enzymatic degradation. Differential s canning calorimetry, optical microscopy, wide-angle X-ray diffraction and s mall-angle X-ray scattering were employed to characterize the PHB films. A decreasing of enzymatic degradation rate was observed with the increasing o f crystallinity and crystal dimension of the PHB films. PHB samples showing the same degree of crystallinity and similar value of lamellar thickness w ere prepared using different isothermal crystallization and annealing tempe ratures. The differences in the enzymatic degradation rate of these films w ere explained in terms of morphological parameters. (C) 1999 Published by E lsevier Science Ltd. All rights reserved.