Optimization of induction conditions
For the optimization of IPTG concentration, after the culture was
transferred to TBSB, IPTG with a final concentration of 0, 0.05, 0.1,
0.2, 0.4, 0.6, 0.8, and 1.0 mM was added to the culture medium. Then,
MWP was kept at 25℃ and 220 rpm for 24 h.
For the optimization of the pre-induction period, three transformants
were picked up for each strain and activated in MWP containing 2 mL LB
medium and 50 mg/L kanamycin at 37 ℃, 220 rpm for 12 h. Then, the
cultures were transferred to 2 mL fresh TBSB medium with a 10% (v/v)
inoculation rate. 0.1 mM IPTG was added to the culture medium at 0, 1,
2, 3, and 4 h after inoculation, respectively. All MWPs were kept at
25℃, 220 rpm for 24 h.