Metabolism of 2,4-dinitrotoluene (2,4-DNT) by Alcaligenes sp. JS867 under oxygen limited conditions


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Abstract

Transformation of 2,4-dinitrotoluene (2,4-DNT) by Alcaligenes JS867 under varying degrees of oxygen limitation was examined. Complete 2,4-DNT removal was observed under oxygen excess with near stoichiometric release (83%) of nitrite. Average kinetic parameters were estimated based on a dual-Monod biokinetic model with 2,4-DNT and O2 as growth limiting substrates. The negative impact of nitrite accumulation on the reaction rate was adequately described by inclusion of a noncompetitive inhibition term for NO2. Under aerobic conditions, μmax, KsDNT, and KiNO were 0.058(0.004) hr−1, 3.3(±1.3) mg 2,4-DNT/L, and 1.2(±pm0.2) hr−1, respectively. At increasing oxygen limitation, rates of 2,4-DNT disappearance and nitrite production decreased and incomplete removal of 2,4-DNT commenced. JS867 was able to use NO2as a terminal electron acceptor when grown on glucose or succinate under anaerobic conditions. However, during growth on 2,4-DNT and under O2-limited conditions, JS867 did not use released nitrite as electron acceptor. The nearly constant molar ratios of DNT removed over NO2released under various degrees of oxygen limitation suggested that oxygenolytic denitration pathways continued. No evidence of nitroreduction was obtained under the examined oligotrophic conditions. JS867 displayed a high affinity for oxygen consumption with KSO2 value of 0.285(±0.198) mg O2/L. Our results indicate that under oligotrophic conditions with 2,4-DNT as dominant carbon source, oxygen availability and nitrite accumulation may limit 2,4-DNT biomineralization, but the accumulation of reduced 2,4-DNT transformation products will be small.

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