reported that improved cellular growth and more biomass production during degradation of petroleum hydrocarbons can or cannot occur, as the metabolic pathways of different microorganisms are versatile. In the presence of other easily metabolizable carbon sources, the shift of metabolic machinery towards biomass production and away from the hydrocarbon degradation may occur. The trend of discrepancies in correlation between biomass production and hydrocarbon biodegradation was observed in this study and has also been reported by Elshafie et al. (2007). Cookson Jr (1995) also reported that the presence of other carbon sources, those which can degrade preferentially over target compound, result in less degradation of targeted contaminant by microorganism.