Isolation of biodemulsifier producing bacteria from petroleum-contaminated deposits of Abadan Oil Refinery

Chemical demulsifiers that are used for breaking water in oil emulsions, are toxic and have adverse side effects for environment. So, biodemulsifiers have been suggested as an environmental friendly alternative. The aim of this study was to achieve biodemulsifier producing bacteria. For this purpose, biodemulsifier producing bacteria were isolated from deposits in oil reservoirs in petroleum refinery through enrichment in saline-based enrichment medium with liquid paraffin and screened in quantitative and qualitative screening methods. Optimum growth condition of the selected isolates as well as the effect of carbon source on biodemulsifier production were assessed and these isolates were identified based on phenotypic methods a sequencing of 16S rRNA gene. As a result, HS20 and HS22 isolates with 71.43 and 85.71percentage demulsification of water in kerosene were identified as Alcaligenes sp. strain HS20 and Alcaligenes sp. strain HS22, respectively. Optimum temperature, pH and nitrogen source for HS20 were as 40°C, 7 and NaNO3 and for HS22 were 35°C, 7 and NH4NO3. The HS20 biodemulsifier was extracellular while in case of HS22 was in both extracellular and cell attached forms. Both isolates were able to produce biodemulsifier in the presence of hydrophilic and/or mixture of hydrophilic and hydrophobic hydrocarbons. The results of this study showed that these isolates have appropriate biodemulsifier production and emulsion breaking. Therefore, evaluation of their potential to improve the breakdown of undesirable water in crude oil emulsions at industrial scale is proposed.