2.3 EGFP intensity measurement
After successful construction in E. coli JM109, all plasmids were
transformed into E. coli BL21. Three transformants were picked up
for each expression strain and activated in 24 deep-well plate
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 LB medium with a
10% (v/v) inoculation rate, and 1 mM IPTG was directly added after
inoculation. After 24 h of induction, the cells were collected and
diluted at about 0.5. The fluorescence intensity was measured by a
fluorescence spectrophotometer at a 488 nm excitation wavelength and a
507 emission wavelength. Each sample’s unit fluorescence intensity was
calculated by normalizing the fluorescence intensity by
OD600.