Comparative studies on emulsification and biodegradation of indigenous crude oils by enriched bacterial culture.

Abstract

Bacteria isolated from oil contaminated soil and cultured on paraffin oil medium, were adapted to various crude oils. The enriched cultures so obtained were used for emulsification of indigenous crude oils under shaking conditions. Varying degrees of emulsification based on visual observation were noted by different cultures, dependent upon the chemical composition of different crude oils. Tando Alum and Khaskheli crude oils were emulsified in 27 and 33 d of incubation respectively, while Joyamair crude oil did not emulsify even after 72 d of incubation. This persistence was found to be mainly due to the low API gravity value i.e., high viscosity, of this oil. Oil from control (uninoculated) and biodegraded flasks was fractionated and quantified by Adsorption and Gas Liquid Chromatographic (GLC) methods. Comparison of different fractions, i.e., saturate, aromatic, NSO (Nitrogen, sulfur, oxygen containing hydrocarbons) revealed that the saturate fraction was preferentially utilized during biodegradation. It was observed that crude oils having greater contents of saturate fraction were better emulsified than crude oils low in this fraction. These bacterial strs in mixed culture utilize different fractions of crude oils in the order of saturate > aromatic > NSO and the persistence was found to be mainly due to high viscosity.