Nanoscaled Processing of Poly[(R)-3-hydroxybutyrate] Single Crystal
by Enzymatic Degradation

Tomohide Murase, Tadahisa Iwata, Yoshiharu Doi

Polymer Chemistry Laboratory,
RIKEN Institute, Hirosawa, Wako-shi, Saitama 351-0198, Japan

Poly[(R)-3-hydroxybutyrate] (P(3HB)) is a biodegradable thermoplastic. The enzymatic degradation of solution-grown P(3HB) single crystals with extracellular polyhydroxybutyrate (PHB) depolymerases has been extensively studied to investigate the degradation mechanism.
In this study, P(3HB) single crystals were adsorbed on highly ordered pyrolytic graphite (HOPG), and the enzymatic degradation was carried out with a PHB depolymerase purified from Alcaligenes faecalis T1. After degradation, rinsing and drying, morphology of a lamella of P(3HB) single crystals on HOPG was observed by atomic force microscopy.
Comblike structure was successfully obtained at the end of a lamella with the enzymatic degradation. The width and the thickness of each fragment of the comb were about 50 nm and 5nm, respectively. In addition, the width of the fragment could be controlled with the molecular weight of P(3HB). The results indicate that enzymatic degradation can be utilized as a tool of nanoscaled processing of biodegradable material.