Figure 3

The effect of the metabolic pathway and expression level of the MVA upper pathway on β-carotene production. A: The effect of metabolic pathway on β-carotene production. The pathway details were described in Figure 1. The β-carotene titer of strain YJM44 harboring the hybrid MVA pathway reached 52.6±1.5 mg/L, which was approximately 49-fold and 3.5-fold higher than that of strains YJM39, which bears the native MEP pathway, and YJM43, which carries the optimized MEP pathway with the overexpression of the DXS and FNI enzymes from B. subtilis and the GPPS2 enzyme from A. grandis, respectively. B: The effect of expression level of the MVA upper pathway on β-carotene production. The MVA upper pathway under the control of the T7 promoter (YJM44) achieved much higher β-carotene production than it did under the control of the araBAD promoter (YJM46). The strain YJM45, using a low copy number plasmid, reached the highest β-carotene production (71.4±4.3 mg/L). The experiment was conducted in triplicate.