Monoclonal strains were selected and cultured in 5 mL resistant medium at 37 °C to OD600=1.2 (about 5 h)
Take 1 mL of bacteria solution with correct sequencing into a 2 mL centrifuge tube, and add an appropriate amount of inducer (such as 1 μL 1M IPTG), take another 1 mL of bacterial liquid into another 2 mL centrifuge tube, without adding inducer, and put them into a shaking table at 16 °C for induction for 5 h.