Cells were separated from the cultivation medium by centrifugation (Hettich Rotina 35R) at 14,000 rpm for 5 min at +4◦C. The harvested cells were washed with sodium phosphate buffer twice in microcentrifuge tubes, kept on ice and then sonicated (SonicsVibra Cell) with a power input to 60 W and a frequency of 20 kHz for5 min. The cell debris was removed by centrifugation at 14,000 rpm for 5 min at +4◦C and the clear supernatant was used to determine the intracellular azoreductase activity.