title: Enzymatic degradation of atactic poly(R,S-3-hydroxybutyrate) induced by amorphous polymers and the enzymatic degradation temperature window of an amorphous polymer system.
abstract: The phase structure and biodegradability were investigated for amorphous blends of chemosynthetic fully amorphous atactic poly(R,S-3-hydroxybutyrate) (a-PHB) with atactic poly(methyl methacrylate) (PMMA) and atactic poly(R,S-lactide) (a-PLA). The differential scanning calorimetry thermal analysis indicated that a-PHB/PMMA blends were partially miscible while a-PHB/a-PLA blends were miscible in the studied composition range. The biodegradations of the blends were carried out in phosphate buffer solution in the presence of bacterial poly(R-3-hydroxybutyrate) extracellular depolymerases purified from Alcaligenes faecalis T1 and P. stutzeri. Although a-PHB in the pure state was not degraded by these depolymerase, it was degraded by blending with PMMA and a-PLA. The results demonstrated that the enzymatic degradation of a-PHB can be induced by amorphous polymers such as PMMA and a-PLA. Also, the biodegradation rate of a-PHB in the blends decreased drastically when the degradation temperature is too much away from the polymer glass transition temperatures. On the basis of these results, a temperature window of the enzymatic degradation was first proposed for the blend and the essence of induced degradation was discussed.
authors.affiliation: Department of Biomolecular Engineering, Tokyo Institute of Technology, Nagatsuta 4259, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: He
authors.forename: X
authors.initials: X
authors.lastname: Shuai
authors.forename: K
authors.initials: K
authors.lastname: Kasuya
authors.forename: Y
authors.initials: Y
authors.lastname: Doi
authors.forename: Y
authors.initials: Y
authors.lastname: Inoue
mesh_terms: D000421:Alcaligenes / Q000201:enzymology; D001673:Biodegradation, Environmental; D002152:Calorimetry, Differential Scanning; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism; D006868:Hydrolysis; D006885:Hydroxybutyrates / Q000737:chemistry* / Q000378:metabolism*; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D011091:Polyesters / Q000737:chemistry* / Q000378:metabolism*; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011549:Pseudomonas / Q000201:enzymology; D013696:Temperature; D000094122:Polyhydroxybutyrates
chemical_list: D002265:Carboxylic Ester Hydrolases; D006885:Hydroxybutyrates; D046911:Macromolecular Substances; D011091:Polyesters; D019904:Polymethyl Methacrylate; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates; C033616:poly(lactide); C022417:poly-beta-hydroxybutyrate depolymerase