Effects of Solid-State Structures on the Enzymatic Degradability of Bacterial Poly(hydroxyalkanoic acids)

Abstract

The effects of solid-state structures on the rate of enzymatic erosion for melt-crystallized films of bacterial poly(hydroxyalkanoic acids) (PHAs) have been studied at 37 °C and pH 7.4 in the aqueous solution of an extracellular PHB depolymerase from Alcaligenes faecalis. In this study, the following PHA homopolymer and copolymers were used; poly(3-hydroxybutyric acid) (P(3HB)), poly(3-hydroxybutyric acid-co-7 mol % 3-hydroxyvaleric acid), poly(3-hydroxybutyric acid-co-22 mol % 3-hydroxyvaleric acid), poly(3-hydroxybutyric acid-co-10 mol % 4-hydroxybutyric acid), poly(3-hydroxybutyric acid-co-4 mol % 3-hydroxyhexanoic acid), and poly(3-hydroxybutyric acid-co-11 mol % 3-hydroxyhexanoic acid). All PHA films were crystallized isothermally at temperatures of 60−140 °C for different periods from the melt. The crystallinity of the films of P(3HB) homopolymer ranged from 53 to 80%, while those of PHA copolymers ranged from 39 to 71%, determined by X-ray crystallography and depending on the crystallization condit...