Screening and Evaluation of Poly(3-hydroxybutyrate) with Rhodococcus equi Using Different Carbon Sources

A process has been developed for the production of poly(3-hydroxybutyrate) (PHB) with bacterium Rhodococcus equi using crude palm kernel oil (CPKO) as a carbon source. Such process will enable the production of biodegradable biopolymers to overcome some of the limitations associated with the use of petroleum-based plastics. A pure isolate was obtained from a fertile soil and was screened using the Nile Red stain for its ability for polyhydroxyalkanoates production. The isolate was identified by morphological characterization and biochemical tests. Identification by 16S rRNA has confirmed the species as Rhodococcus equi. Different carbon sources were used in an attempt to find the best one for the biosynthesis of PHB. The microscopic observations of PHB inside the bacteria were checked by the phase-contrast light microscope which showed a bright appearance. Moreover, the fluorescent microscope showed a bright orange fluorescence, and the transmission electron microscope showed white PHB granules with different sizes and different numbers within the bacteria cells. Rhodococcus equi gave the maximum cell dry mass as 1.43 g/L with the maximum PHB content as 38.1 % by weight when CPKO (1 %) was used as a carbon source.