Cupriavidus eutrophus B10646 was used to synthesize a series of polyhydroxyalkanoate (PHA) quaterpolymers composed of the short-chain-length 3-hydroxybutyrate (3HB), 4-hydroxybutyrate (4HB), and 3-hydroxyvalerate (3HV) and the medium-chain-length 3-hydroxyhexanoate (3HHx). The molar fraction of 3HB in the quaterpolymers varied between 63.5 and 93.1 mol.%, 3HV - between 1.1 and 24.6 mol.%, 4HB - between 2.4 and 15.6 mol.%, and 3HHx - between 0.4 and 4.8 mol.%. The properties of PHA quaterpolymers were significantly different from those of the P(3HB) homopolymer: they had much lower degrees of crystallinity (up to 30-45%), and lower melting points and thermal decomposition temperatures, with the interval between these temperatures remaining practically unchanged. Films prepared from PHA quaterpolymers were rougher and more porous than P(3HB) films; they showed higher values of elongation at break (up to 6-113%), i.e. were more elastic. Films prepared from PHA quaterpolymers were biocompatible and had no toxic effect on mouse fibroblast NIH 3T3 cells. (C) 2016 Elsevier Ltd. All rights reserved.