Isolation of Oil Degrading Bacteria from Oil Contaminated Soil around the Oil Refinery and Petrochemical plants of Tabriz and Identification of the efficient Bacteria

Abstract

Petroleum hydrocarbons are the most common organic contaminants in water and soil ecosystems around the world. Application of soil microorganisms is one of the cost-effective and environmentally friendly approaches to remove or reduce the oil pollution. Isolation and assessment of oil-degrading bacteria is the first step in bioremediation. Accordingly, the aim of this study was isolation of crude oil degrading (COD) bacteria from contaminated soil samples around the refinery and petrochemical plants of Tabriz and assessment of their ability in oil degradation. Based on bacterial growth indicators (e.g. optical density (OD) and microbial biomass, percent of crude oil degradation and production of biosurfactant), 20 efficient isolates were selected among the 60 isolates using carbon free minimal medium (MSM) supplemented with crude oil. The most efficient strains that had the highest OD, microbial biomass and percentage of oil biodegradation with biosurfactant production ability were included isolates COD2-1, COD1-5, COD4-3, COD4-2, COD9-3, COD6-3, COD7-1, COD3-1, COD1-1 and COD8-1. While other efficient isolates (COD1-4, COD5-6, COD4-5, COD7-3, COD4-6, COD6-1, COD6-4, COD2-3, COD8-2 and COD3-3) did not have the ability of biosurfactant production. The results of molecular identification of bacteria showed that these isolates belonged to the genus and species Stenotrophomonas sp., Achromobacter sp., Psedochrobactrum sp., Arthrobacter sp., Shewanella sp., Alcaligenes sp., Pseudomonas sp. and Acinetobacter baumannii. Among these isolates, the genus Stenotrophomonas sp., Psedochrobactrum sp., Arthrobacter sp. and Shewanella sp. with high quantitative and qualitative indices were introduced for bioremediation experiments in contaminated soil.