Biosynthesis of P3HBV-b-P3HB-b-P3HBV Triblock Copolymer by Ralstonia eutropha
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Poly(3-hydroxybutyrate-c-3-hydroxyvalerate)(P3HBV)-b-poly(3-hydroxybutyrate) (P3HB)-b-P3HBV triblock copolymer biosynthesized from Ralstonia eutropha was investigated with respect to crystallization and compared with P3HBV-b-P3HB diblock copolymer. First, P3HBV and second, P3HB blocks lengths were fixed, and the third P3HBV block length was changed by regulating the cultivation time. The fraction of P3HB sandwiched by P3HBV blocks was between 50.0 and 86.4%. For the triblock copolymer with a longer third P3HBV block, there was no exothermic crystallization peak cooling from the melt at 200 °C. However, the diblock copolymer provided P3HB crystallization. Therefore, the P3HB block sandwiched by P3HBV with a sufficiently long cultivation time prevented crystallization during the melt-cooling process. Although the crystallization was prevented just after cooling from the melt for the triblock copolymer, it was gradually promoted within a few hours. This shows that the crystallization rate of P3HB is very low because of P3HV blocks.
KeywordsPoly(3-hydroxybutyrate) Poly(3-hydroxyvalerate) Biosynthesis Triblock copolymer Crystallization
This work was carried out by the financial support from Ryukoku University.