Metabolic engineering for 5-aminolevulinic acid production by Escherichia coli carrying Rhodobacter sphaeroides hemA
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Engineered E. coli strains were constructed to carry the Rhodobacter sphaeroides hemA gene. Succinate, IPTG, and glucose concentration, and IPTG addition time were studied for the optimization of Aminolevulinate synthase production using one way, one-at-a-time, and 2 4 full factorial design in E. coli MG1655/pTrc99A-hemA and AFP111/pTrc99A-hemA. Aminolevulinate synthase activities of 293.6 mU/mg protein and 140.4 mU/mg protein were obtained in MG1655/pTrc99A-hemA and AFP111/pTrc99A-hemA, respectively, under optimized conditions: 3.0-5.0 g/L succinate and 0.05mM IPTG added initially. Fed-batch fermentations with media containing either tryptone or NH4Cl as nitrogen source in E. coli MG1655/pTrc99A-hemA and CGSC4676/pTrc99A-hemA provided with up to 4.0 g/L 5-aminolevulinic acid and 0.5 g/L aminoacetone. ALA specific productivities of 0.07 g/g dry cell h or 0.12 g/g dry cell h were obtained in fermentations with media containing tryptone or NH4Cl, respectively.