Fig. 2

Base substitution on argA increased putrescine production. Putrescine concentration in the supernatant of strains harboring plasmids with different mutant argA: KT207 (argA^{ATG Y19C}), KT208 (argA^{GTG Y19C}), KT209 (argA^{ATG Y19}), and KT210 (argA^{GTG Y19}). The strains were grown in LB medium supplemented with 100 μg/mL of ampicillin at 37 °C for 48 h with reciprocal shaking at 120 rpm. When the OD₆₀₀ reached 0.4, 0.02 mM IPTG was added. **, p < 0.01; ***, p < 0.001. Data shown are averages ± standard deviations, and culture experiments were performed in triplicate