Isolation of bacteria that degrade long-chain alkanes from oil contaminated soil

Aim and Paraffins are high molecular weight hydrocarbons and in the reservoir، under high- temperature/pressure conditions remain in a state of equilibrium. However، as the crude oil is pumped out to the surface، temperature and pressure are reduced. Below the cloud point، the paraffinic hydrocarbons precipitate out of the crude oil and form deposits on the oil production systems. This problems are usually mitigated by thermal fluid treatments، pigging or using chemicals and solvents. While most of these remedies are in use، they have certain disadvantages. Moreover، these remedial options are expensive. A microbial intervention to prevent paraffin deposition، is a non hazardous and economically viable approach. This investigation was aimed at finding a bacterial strain that being able to effectively degrade tetracosane. Soil samples were collected from oil contaminated soil near Tehran refinery. Samples were transferred into 40 ml sterile mineral salts medium containing tetracosane as the sole source of carbon and energy. By a multi step enrichment and screening technique a bacterium was isolated and by morphological characteristics، biochemical tests and phylogenetic methods، it was identified as the Mycobacterium genus. This strain was able to use tetracosane as the sole source of carbon and energy. Our results showed the selected strain grow well in pH range of 4-9 and temperature range of 30 - 40 °C with optimal growth at 35°C، had an acceptable growth at 5% NaCl and was able to degrade 80 percent of the tetracosane within 24 days. According to the rate of tetracosane decomposition by this bacteria under conditions listed، its application can be profitable in preventing paraffin deposition. Further investigation in physical model is required to confirm the ability of the strain in wax deposit mitigation from oil wells.