Removal of toxic methyl tert-butyl ether by Naphthalene degradating bacterium isolated from freshwater

Introduction and objective: Naphthalene as a cyclic aromatic hydrocarbon is one of the major part of pollution in oil-contaminated environments. Methyl tert-butyl ether (MTBE), an additive to gasoline, is widely used. MTBE is highly water soluble, toxic and causes cancer. Naphthalene degraders have gene for co-oxidation of other toxic compounds therefore Naphthalene degrader could utilize and oxidize other toxic contaminant. The aim of this study is to isolate and identify bacteria that could degrade Naphthalene and MTBE as a circular and liner component respectively.

Material and methods: Freshwater was contaminated with Naphthalene and after several subcultures, strain SA86 was isolated and identified as Pseudomonas by biochemical test. Then bacterium was grown in culture with determined amount (1000ppm) of Naphthalene and the disappearance of Naphthalene was monitored with Gas Chromatography (GC) after six days. Then inoculate of the above bacteria was transferred to Teflon cape tube containing 500ppm MTBE and incubated for 24h. The removal of MTBE was measured by GC.

Results: The results showed that strain Pseudomonas (SA86) can degrade 99% of Naphthalene during six days incubation period. In addition this strain can remove 70% of MTBE. Meanwhile by products resulted from oxidation of MTBE were not observed.

Conclusion: The results emphasise that Naphthalene degrading bacterium isolated in this study can remove MTBE as well as Naphthalene, while there are different in their chemical structures. Obviously Naphthalene   induced the MTBE oxidation enzymes.   

Significance and impact of the study: Usually co-metabolism reaction is necessary for MTBE oxidation. However, here it is shown that Naphthalene grown cells are useful for MTBE removal with no co-metabolism reaction.