BIODEGRADATION OF NITROBENZENE BY ITS SIMULTANEOUS REDUCTION INTO ANILINE AND MINERALIZATION OF THE ANILINE FORMED

By mixing through a three-reactor system a nitroreducing consortium an d an aniline-degrading Comamonas acidovorans, a mixed population was f ormed which was able to mineralize the nitroaromatic compound nitroben zene via aniline, its corresponding aminoaromatic compound. The behavi or of the mixed population was characterized in batch culture. In the first step, nitrobenzene was reduced to aniline by the reductive conso rtium and, in the second, oxidative step, aniline was mineralized via catechol and meta cleavage. Even though these two steps may seem incom patible in terms of required redox conditions, they were made to coexi st in a single, simple reactor. However, when aeration was optimum for growth, only 16% of the 0.5 mM nitrobenzene introduced was mineralize d. Decreasing the aeration led to an increase in the amount of nitrobe nzene reduced and decreased its volatilized fraction. A decrease in ae ration did not slow down aniline mineralization, although the latter i s catalyzed by dioxygenases. This mixed population is thus able to rem ediate nitrobenzene and also aniline, which is often found with the fo rmer in the environment. Using C. acidovorans, which also degrades met hylanilines, or other aminoaromatic-compound-degrading organisms, this strategy should be applicable to mineralizing more complex nitroaroma tic compounds, like nitrotoluenes or dinitrotoluenes.