Production of medium chain length polyhydroxyalkanoates from cupriavidus necator with beeswax hydrolyzates as carbon source

Abstract

This study demonstrates that using beeswax hydrolyzates (Hw), short- or mediumchain-length polyhydroxyalkanoates (scl-mcl-PHA) can be obtained by a three stages fed-batch fermentation system. The fed batch fermentations were conducted with a strain ofCupriavidus necator. Glucose and ammonium sulphate as carbon and nitrogen sources, respectively, were used in a fist and second culture stages. In the third stage (production of scl-mcl-PHA) a fresh medium was fed with Hw as a carbon source at a concentration of 5 g/L, obtaining 8.91 g/L of intracellular scl-mcl-PHA and 13.64 g/L of biomass, which resulted in 65.3 % w/w of scl-mcl-PHA. Using nuclear magnetic resonance, the presence of scl and mcl monomers, 3-hydroxybutyrate (3HB) and 3-hydroxydecanoate (3HD) was determined. The percentage of comonomer incorporation different to 3HB was 4.6 mol %. A glass transition temperature (Tg) of –50 ºC and a melting temperature (Tm) of 79.8 ºC were determined for the scl-mcl-PHA (3HB-co-3HDD).