2.3. Whole-cell reaction
The harvested BL21 Star (DE3) cells expressing LCD were used for the whole-cell reaction. For l-PA production, 200 mM l-lysine was used as substrate, and 150 mM potassium phosphate buffer (pH 7) was used to buffer the mixture. To enhance cell permeability, 0.1% triton X-100 was added. FeSO4 at 20 mM was added as source of iron. Distilled water was added to the reaction mixture containing harvested cells with an OD600 of 50 to prepare a total volume of 400 μL. The mixture was titrated to pH 7.5 with 2 N NaOH. The reaction was conducted at 37 °C with gentle shaking (40–50 rpm). After reaction, 100 μL of each sample was collected and heated at 95 °C for 5 min to complete the reaction. Inactivated cells were eliminated by centrifugation at 13,000 rpm, and the supernatant was diluted to an appropriate concentration for analysis.