Transformation of 2,4,6-trinitrotoluene (TNT) by immobilized Phanerochaetechrysosporium under fed-batch and continuous TNT feeding conditions

The cometabolic transformation of 2,4,6-trinitrotoluene (TNT) by an immobil ized Phanerochaete chrysosporium culture was investigated under different T NT and/or glycerol feeding conditions in a 5-L reactor. In the fed-batch fe eding mode, as a result of four spiking events at an average feeding rate o f 20 mg TNT L-1 d(-1) and 250 mg glycerol L-1 d(-1), the initial TNT transf ormation rate and the glycerol uptake rate of the 7-day-old immobilized cel l culture were 2.41 mg L-1 h(-1) and 16.6 mg L-1 h(-1), respectively. There after, the TNT fed into the reactor depicted a negative effect on the cell physiology of P, chrysosporium, i.e., both rates decreased constantly. At 3 2 mg TNT L-1 d(-1) feeding rate, also in the presence of glycerol (200 mg L -1 d(-1)), this effect on the fungal cell metabolism was even more signific ant. When TNT was fed alone at 3.7 mg L-1 d(-1), it showed an initial 0.75 mg L-1 h(-1) rate of TNT transformation, i.e., one-third the initial level observed in the presence of glycerol. In contrast, in the continuous feedin g mode (dilution rate, D = 0.11 d(-1)), at 5.5 mg TNT L-1 d(-1) and 220 mg glycerol L-1 d(-1), the immobilized cell culture exhibited a constant TNT t ransformation rate for cultivation periods of 50 and 61 days, under uncontr olled and controlled pH conditions, respectively. Thereafter, during the la tter experiment, 100% TNT biotransformation was achieved at 1,100 mg L-1 d( -1) glycerol feeding rate. Immobilized cells (115-day-old), sampled from a continuous TNT feeding experiment, mineralized [C-14]-TNT to a level of 15. 3% following a 41-day incubation period in a microcosm. (C) 2001 John Wiley & Sons, Inc.*