Thermostable Biopolyester

Abstract

A biopolyester which is poly(3-hydroxyalkanoate) or poly(3-hydroxyalkanoate) copolymer and has a reduced calcium content. It has improved thermal stability due to the reduced calcium content.

1 . A biopolyester which is selected from poly(3-hydroxyalkanoate) and poly(3-hydroxyalkanoate) copolymer, wherein said biopolyester has a calcium content of 120 ppm or less. 
     
     
         2 . The biopolyester according to  claim 1 , wherein the biopolyester is poly(3-hydroxybutyrate). 
     
     
         3 . The biopolyester according to  claim 1 , wherein the biopolyester is poly(3-hydroxybutyrate)-(3-hydroxyvalreate). 
     
     
         4 . A method of producing a thermostable biopolyester, comprising removing calcium from poly(3-hydroxyalkanoate) or poly(3-hydroxyalkanoate) copolymer which is produced by a microorganism to obtain poly(3-hydroxyalkanoate) or poly(3-hydroxyalkanoate) copolymer having a reduced calcium content. 
     
     
         5 . The method according to  claim 4 , wherein the calcium is removed by dissolving the poly(3-hydroxyalkanoate) or the poly(3-hydroxyalkanoate) copolymer which is produced by a microorganism, and acidifying the obtained solution.