AEROBIC BIODEGRADATION OF BENZENE, TOLUENE,
ETHYLBENZENE, AND XYLENES BY HALOPHILIC AND
HALOTOLERANT BACTERIA
Babu Z. Fathepure*
Carla A. Nicholson
Oklahoma State University
Dept. of Microbiology and Molecular Genetics
307 Life Science East
Oklahoma State University
Stillwater, OK 74078
Voice: 405-744-7764
Fax: 405-744-6790
E-mail: fathepu@okstate.edu
Since conventional microbiological treatment processes do not function at high salt concentrations, bioremediation of oilfield brine can only be accomplished by stimulating either indigenous bacteria or through bioaugmentation of halophiles capable of degrading fuel hydrocarbons. Microcosms were established with brine soil obtained from different oilfields and other salterns in Oklahoma. Our preliminary studies showed that 14C-benzene was mineralized to 14CO2 under both aerobic and anaerobic conditions. We have obtained highly enriched microbial consortia from brine soil by repeated feeding with benzene and transferring sediment-free cultures to fresh mineral salts medium. Molecular characterization of the enrichment culture using denaturing gradient gel electrophoresis (DGGE) and 16S rDNA revealed that the Marinobacter sp. was the dominant organism. These enrichments rapidly degraded BTEX in the presence of high concentrations of NaCl and little degradation occurred when no salt was added. Attempts to enhance rate of benzene degradation through the addition of organic stimulants have met with little success. The impact of salt on microbial diversity of the benzene degrading enrichment was assessed by DGGE. The analysis shows that different organisms dominate at different salt concentrations and the organisms at high salt, 3 or 4 M NaCl showed low sequence match to the known organisms in the RDP (Ribosomal Database Project).