Microbial degradation of benzene, toluene, ethylbenzene and xylene isomers (BTEX) contaminated groundwater in Korea.

A mixed culture derived from a gasoline-contaminated aquifer in Korea was enriched on toluene at 25 degrees C. A study was conducted to characterize the substrate interaction of BTEX by toluene-enriched consortia and determine the effects of initial BTEX concentration on BTEX degradation. Substrate degradation patterns in individual aromatics were found to differ significantly from patterns for aromatics in mixtures. In the experiment of a single substrate, toluene was degraded fastest, followed by benzene, ethylbenzene, and the xylenes. In BTEX mixtures, degradation followed the order of toluene, ethylbenzene, benzene, and the xylenes. The studies conducting with toluene-enriched consortia evaluated substrate interactions by the concurrent presence of multiple BTEX compounds and revealed a range of substrate interaction patterns including no interaction, stimulation, inhibition, and cometabolism. The simultaneous presence of benzene and toluene were degraded with a slight inhibitory effect on each other. Ethylbenzene was shown to be the most potent inhibitor of BTEX degradation. p-xylene also inhibited the degradation of benzene, toluene, and ethylbenzene, whereas the presence of either benzene or toluene enhanced the degradation of ethylbenzene and the xylenes.