title: Comonomer compositional distribution, physical properties, and enzymatic degradability of bacterial poly(3-hydroxybutyrate-co-3-hydroxy-4-methylvalerate) copolyesters.
abstract: Poly(3-hydroxybutyrate-co-3-hydroxy-4-methylvalerate) (P(3HB-co-3H4MV)) was synthesized by using Ralstonia eutropha strain PHB(-)4 (PHA-negative mutant) harboring with the N149S/D171G double mutation of PHA synthase gene from Aeromonas caviae (PhaC(Ac) NSDG mutant) with 4-methylvaleric acid and fructose as the carbon sources. Because the microbially synthesized P(3HB-co-3H4MV) samples were found to have broad comonomer compositional distribution, P(3HB-co-3H4MV) samples with 3H4MV content of 7, 11, and 35 mol % were fractionated into several fractions with different comonomer composition ranging from 2 to 47 mol % by using a chloroform/n-hexane mixture. It was confirmed that a series of well-fractionated P(3HB-co-3H4MV) samples had a statistically random distribution. Physical properties and structure of the fractionated P(3HB-co-3H4MV) random copolymers were investigated. Both the melting temperature and glass-transition temperature of P(3HB-co-3H4MV) copolymers decreased with an increase in the 3H4MV composition. The degree of X-ray crystallinity of fractionated P(3HB-co-3H4MV) films decreased from 60 to 13% as the 3H4MV fraction increased from 0 to 39 mol %. Enzymatic degradation test for fractionated P(3HB-co-3H4MV) films was carried out at 37 degrees C in the presence of PHB depolymerase from Ralstonia pickettii T1. The rates of enzymatic erosion markedly increased with an increase in the 3H4MV composition to reach the highest one at 7 mol % of 3H4MV, followed by a decrease in erosion rate.
authors.affiliation: Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan.
authors.forename: Nuttapol
authors.initials: N
authors.lastname: Tanadchangsaeng
authors.forename: Takeharu
authors.initials: T
authors.lastname: Tsuge
authors.forename: Hideki
authors.initials: H
authors.lastname: Abe
mesh_terms: D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics; D000333:Aeromonas / Q000201:enzymology / Q000235:genetics; D001672:Biocompatible Materials / Q000737:chemistry*; D005591:Chemical Fractionation; D055598:Chemical Phenomena; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D020118:Cupriavidus necator / Q000201:enzymology / Q000235:genetics; D008970:Molecular Weight; D009154:Mutation; D011091:Polyesters / Q000737:chemistry* / Q000378:metabolism*; D054813:Polyhydroxyalkanoates / Q000096:biosynthesis* / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D000094122:Polyhydroxybutyrates
chemical_list: D000217:Acyltransferases; D001672:Biocompatible Materials; D011091:Polyesters; D054813:Polyhydroxyalkanoates; C553274:poly(3-hydroxybutyrate-co-3-hydroxy-4-methylvalerate); D000094122:Polyhydroxybutyrates; C077225:poly(3-hydroxyalkanoic acid) synthase; C060970:poly-beta-hydroxybutyrate polymerase