Bioconversion of oily bilge waste to polyhydroxybutyrate (PHB) by marine Ochrobactrum intermedium

A bacterial strain capable of producing polyhydroxybutyrate (PHB) utilizing hydrocarbon wastes was isolated from oily bilge waste contaminated sea water. The isolate was identified as Ochrobactrum intermedium based on biochemical, 16S rRNA partial gene sequencing. Tolerance and growth of the isolate with different hydrocarbons were analysed. Hydrocarbon degrading ability of O.intermedium was determined by emulsification index and cell surface hydrophobicity analysis. The isolate utilized aliphatic hydrocarbons efficiently than aromatic hydrocarbons. PHB accumulation by the isolate was confirmed by Sudan black and Nile red staining. FTIR, 1H and 13C NMR scans confirm the polymer to be of poly3-hydroxybutyrate. Optimization of Bushnell Hass (BH) medium constituents was carried out by 2 level factorial design and response surface methodology (RSM). Interactive influence of variables having high t-values was analysed by 23 central composite design for the enhancement of PHB production. Optimization of BH medium composition resulted in 37.00% increase in PHB accumulation.