Comparison of Dinitrotoluene Degradation by a Mixed Culture in Aqueous Batch System

Abstract

A mixed culture, enriched from nitrotoluenes -contaminated aged -soil from an ammunition plant in the Czech Republic, was used to study biodegradation of 2,4- dinitrotoluene (2,4-DNT) and 2,6-dinitrotoluene (2,6-DNT) in aqueous media under aerobic conditions. The study was conducted in shake flasks with mineral salt medium with or without additional carbon and energy source. The mineral salt medium was supplemented with either glycerol or succinate as t he primary carbon and energy source. When glycerol supplementation was used with 5.2 mg.L-1 initial concentrations of DNT, the results showed total disappearance of 2,4 -DNT in 6 days and that of 2,6 -DNT in 10 days. With succinate as the carbon and energy source, total disappearance of 2,4 -DNT was observed in 10 days, but the disappearance of 2,6 -DNT was poor. One or more metabolites also accumulated in the medium. After six months of a selection pressure by DNTs, the mixed culture was still able to degrade 2,4-DNT almost completely; its ability to degrade 2,6 -DNT in basal salt medium also increased. Also no intermediates accumulated in the medium. When the dinitrotoluenes were used as the sole source of C -, N- and energy, ∼ 40 % of each DNT was removed within 4 days. However, uptake of 2,4 -DNT showed a lag phase and one unidentified intermediate accumulated in the medium. 2,6-DNT uptake did not show any lag-phase and no intermediate accumulated in the medium.