BACKGROUNDP(3HB-co-3HHx) copolymers are very promising biomaterials. The main challenge in the production of these polymers is to simultaneously achieve high cell biomass; high P(3HB-co-3HHx) content; and high molar fraction of 3HHx in P(3HB-co-3HHx). The most common approach to production of these copolymers is the use of recombinant bacterial strains. The purpose of this study was to optimize the process of production of P(3HB-co-3HHx) copolymers containing high molar fractions of 3HHx by using the wild-type strain Cupriavidus eutrophusB10646. RESULTSKinetic properties of C. eutrophusB10646 were studied during cultivation of the cells on substrates necessary for P(3HB-co-3HHx) synthesis: glucose, nitrogen, sodium hexanoate, and sodium acrylate. The physiological ranges of their effects were determined experimentally, and C. eutrophusB10646 was grown in culture media with different dosages of these substrates. P(3HB-co-3HHx) copolymers with different molar fractions of 3HHx, including high ones (12 to 68%), were synthesized, and their physicochemical and mechanical properties were investigated. CONCLUSIONFor the first time, cultivation conditions of Cupriavidus eutrophusB10646 enabled production of high biomass yields (5-6gL(-1)) and high content of the polymer (60-75%) that contained high 3HHx molar fraction. By varying the 3HB/3HHx ratio, one can change physicochemical and mechanical properties of P(3HB-co-3HHx) copolymers. (c) 2014 Society of Chemical Industry