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 of Cupriavidus necator. Glucose and ammonium sulphate as carbon and nitrogen sources, respectively, were used in a first 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).Palabras clave: biopolímeros, DSC, mcl-PHA, RMN, fermentación lote alimentado RESUMEN Este estudio demuestra que mediante el uso de hidrolizados de cera de abejas (Hw) pueden obtenerse polihidroxialcanoatos de cadena corta o media (scl-mcl-PHA), mediante un sistema de fermentación por lote alimentado de tres etapas. Las fermentaciones por lote alimentado se llevaron a cabo con una cepa de Cupriavidus necator. Se usaron glucosa y sulfato de amonio como fuentes de carbono y nitrógeno, respectivamente, en una primera y segunda etapas de cultivo. En la tercera etapa (producción de scl-mcl-PHA) se alimentó medio fresco con Hw como fuente de carbono a una concentración