Production of polyhydroxybutyrate from wheat bran hydrolysate using Ralstonia eutropha through microbial fermentation

•The first report on converting wheat bran to PHB using cellulase and β - glucosidase.•The sugar concentration and yield was about 62.91 g/L and 629.1 mg/g wheat bran.•No reduction in DCW and PHB while using the hydrolysate without detoxification.•DCW, PHB content and productivity was higher for wheat bran than other biomass.•Wheat bran could be a potential feedstock for PHB as it is not require detoxification.

The increasing global demand for sustainable resources necessitates the complete utilization of feedstock. Wheat bran consists of significant amount of cellulose and hemicellulose which can be used as a renewable resource for production of fermentable sugars. In this study, alkaline pretreated wheat bran was enzymatically hydrolyzed using cellulase of Trichoderma reesei (37 FPU/g) and β - glucosidase of Aspergillus niger (50 CBU/g). Among the nitrogen sources tested, ammonium sulphate was identified as best nitrogen source for the production of polyhydroxybutyrate (PHB). The overall sugar concentration was about 62.91 g/L with the corresponding sugar yield of 629.1 mg/g wheat bran and the sugars released were mainly composed of glucose (48.35 g/L) and xylose (14.56 g/L). The PHB producing mutant strain, Ralstonia eutropha NCIMB 11599 grown in wheat bran hydrolysate produced cell density, PHB and yield of 24.5 g/L, 62.5%, and 0.319 g/g sugar respectively, with a productivity of 0. 0.255 g/L/h. Thus, the results suggested that the wheat bran could be a potential alternative feedstock as it does not require any detoxification due to less inhibitory compounds for production of high cell density with significant amount of polyhydroxybutyrate.