Vine-Twining Inclusion Behavior of Amylose towards Hydrophobic Polyester, Poly(β-propiolactone), in Glucan Phosphorylase-Catalyzed Enzymatic Polymerization

This study investigates inclusion behavior of amylose towards, poly(β-propiolactone) (PPL), that is a hydrophobic polyester, via the vine-twining process in glucan phosphorylase (GP, isolated from thermophilic bacteria, Aquifex aeolicus VF5)-catalyzed enzymatic polymerization. As a result of poor dispersibility of PPL in sodium acetate buffer, the enzymatically produced amylose by GP catalysis incompletely included PPL in the buffer media under the general vine-twining polymerization conditions. Alternatively, we employed an ethyl acetate-sodium acetate buffer emulsion system with dispersing PPL as the media for vine-twining polymerization. Accordingly, the GP (from thermophilic bacteria)-catalyzed enzymatic polymerization of an α-d-glucose 1-phosphate monomer from a maltoheptaose primer was performed at 50 °C for 48 h in the prepared emulsion to efficiently form the inclusion complex. The powder X-ray diffraction profile of the precipitated product suggested that the amylose-PPL inclusion complex was mostly produced in the above system. The ¹H NMR spectrum of the product also supported the inclusion complex structure, where a calculation based on an integrated ratio of signals indicated an almost perfect inclusion of PPL in the amylosic cavity. The prevention of crystallization of PPL in the product was suggested by IR analysis, because it was surrounded by the amylosic chains due to the inclusion complex structure.