Über die Depolymerisierung von Poly-(R)-3-hydroxy-buttersäureester (PHB)

On the Depolymerization of Poly-(R)-3-hydroxy-butanoate (PHB) From cell-free PHB or from dried cells of Alcaligenes eutrophus H 16, which had been grown in an aqueous fructose solution, enantiomerically pure methyl, ethyl, butyl or β-methoxyethyl (R)-3-hydroxy-butanoates are obtained in yields ranging from 75–90% (0.1 to 70 g scale). The depolymerization is achieved by heating the PHB-containing materials to temperatures of 80–160° in the corresponding alcohol with or without the cosolvent dichloroethane in the presence of either sulfuric acid or tetraethoxytitanium catalyst. Since (S)-3-hydroxy-butanoates are also readily obtained (by yeast reduction of aceto-acetates), starting materials derived from 3-hydroxy-butyric acid now belong to the especially useful group of synthetic building blocks which are available in both enantiomeric forms.