KINETICS OF TOLUENE DEGRADATION BY A NITRATE-REDUCING BACTERIUM ISOLATED FROM A GROUNDWATER AQUIFER

Groundwater from a xylene-contaminated aquifer was enriched in the lab oratory in the presence of toluene, xylenes, ethylbenzene, and benzene . A pure culture that degrades toluene and m-xylene under nitrate-redu cing conditions was isolated. Fatty acid analysis, 16S rRNA sequencing , and morphological traits indicate that the isolate was a strain of A zoarcus tolulyticus. The kinetics of toluene degradation under nitrate -reducing conditions by this isolate was determined. Nitrate reduction does not proceed beyond nitrite. Nitrate and toluene are substrate li miting at low concentrations, whereas toluene, nitrate, and nitrite ar e inhibitory at high concentrations. Several inhibition models were co mpared to experimental data to represent inhibition by these substrate s. A kinetic model for toluene and nitrate degradation as well as for cell growth and nitrite production was developed and compared to exper imental data. The results of this work may find important application in the remediation of groundwater aquifers contaminated with aromatic hydrocarbons. (C) 1997 John Wiley & Sons, Inc.