Isolation of MTBE degrading bacteria from polluted soil

Methyl Tert-Butyl Ether (MTBE) is one of the ether oxygenates which its use has been increased within the last thirty years. The contamination of groundwater by MTBE is one of the most serious environmental problems around the world. Biodegradation is a method that can be a good alternative to chemical methods for the removal of MTBE. The aim of this study was isolation of MTBE degrading bacteria from polluted area in order to further investigation of bioremediation processes.MATERIALS AND METHODS: Soil samples were separately collected from 3 sites of gasoline and MTBE discharge in Isfahan-Iran refinery and mixed together. Soil sample was analyzed for soil texture, soil moisture, percentage of organic matter, Electrical conductivity (EC), pH and MTBE concentration. Heterotrophic and MTBE degrading bacterial population were enumerated by spread plate method. Isolation of MTBE degrading bacteria was performed by enrichment culture technique in basal salt medium supplemented with 25 ppm MTBE, and purification was done by streak plate method on nutrient agar. The MTBE tolerance levels of pure colonies were also tested in presence of 25- 1600 ppm of MTBE.RESULTS AND DISCUSSION: Results showed that, pH, EC, organic matter and texture of soil were 7, 2.28 ds/m, 2.13% and loamy sand respectively. Moisture was 30% and MTBE concentration in soil was 321.91 (ng/g soil). Heterotrophic bacterial population was 15×106 CFU/g and MTBE degrading bacterial population was 1.16 ×106 CFU/g so, 7.42% of soil heterotrophic bacterial population showed the MTBE degrading ability which 90.9% of them were gram negative. It can be concluded that some of bacteria presented in polluted environment have the ability to degrade xenobiotic compounds such as MTBE. These bacteria can be isolated and used for bioremediation of other polluted areas.

Keywords:

MTBE , Heterotrophic bacteria , biodegradation , groundwater