Transformation of 2,4,6‐trinitrotoluene (TNT) by immobilized Phanerochaete chrysosporium under fed‐batch and continuous TNT feeding conditions

The cometabolic transformation of 2,4,6‐trinitrotoluene (TNT) by an immobilized Phanerochaete chrysosporium culture was investigated under different TNT and/or glycerol feeding conditions in a 5‐L reactor. In the fed‐batch feeding mode, as a result of four spiking events at an average feeding rate of 20 mg TNT L −1 d −1 and 250 mg glycerol L −1 d −1 , the initial TNT transformation rate and the glycerol uptake rate of the 7‐day‐old immobilized cell culture were 2.41 mg L −1 h −1 and 16.6 mg L −1 h −1 , respectively. Thereafter, the TNT fed into the reactor depicted a negative effect on the cell physiology of P. chrysosporium , i.e., both rates decreased constantly. At 32 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 significant. 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 feeding 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 transformation rate for cultivation periods of 50 and 61 days, under uncontrolled and controlled pH conditions, respectively. Thereafter, during the latter 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 [ 14 C]‐TNT to a level of 15.3% following a 41‐day incubation period in a microcosm. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 73: 271–281, 2001.