Bioremediation of methyl tertiary-butyl ether (MTBE) by three pure bacterial cultures

Bioremediation of groundwater and soil contamination is more economical thanphysicochemical remediation. The present study focused on the bioremediation capability of twobacterial species (Klebsiella planticola and Enterobacter cloacae) from the family Enterobacteriaceae.These bacteria have been identified as new species with capability of degrading methyl tertiary-butylether (MTBE). In order to enhance their degradation capability, selected concentrations and retentiontime were investigated.Methods: The bacteria were cultured on the nutrient agar (NA) medium at room temperature. pH ofthe medium was adjusted to 7. The medium was autoclaved at 121°C for 15 minutes and incubated for24 hours at 35°C. After 24 hours, the mixture was inoculated into 50 mL of Luria Bertani (LB) liquidmedium containing 50 and 150 ppm MTBE. The cultures were incubated for 2 and 5 days at 35°C andshacked on a shaker at 150 rpm. Cell concentrations of the bacteria in pure culture were determined fromthe optical density at 600 nm using a UV–VIS spectrophotometer. Then, the culture was centrifuged at3800 rpm for 20 minutes. In the next step, the MTBE concentration in the supernatant was measured bygas chromatography/mass spectrometry (GC/MS, Agilent Technologies, 5975, US10304411, 5.02.07).Results: The results showed that both strains are able to grow in the presence of 50 and 150 ppm MTBE.In the best conditions, when cell density was 3×108 CFU/mL during 5 days, the highest rate of MTBEdegradation for K. planticola and E. cloacae, was 43% and 40%, respectively. It was also revealed thatEscherichia coli can degrade 50 and 150 ppm MTBE about 19.8% and 13.65%, respectively.Conclusion: It seems that E. coli can be a good candidate for MTBE degradation at high concentrationsfor a time longer than that in the present study. It was also found that the species have high performanceat 50 ppm than 150 ppm. So, these bacteria can remove MTBE from the environment.

Keywords:

Biodegradation , Klebsiella planticola , Enterobacter cloacae , Escherichia coli , methyl tertiarybutyl ether