Abstract: 5-aminolevulinic acid（ALA）is a natural non-protein amino acid and has been widely applied in agriculture and medicine. This study aimed to construct the systhesis pathway of C4 ALA in Corynebacterium glutamicum and optimize its fermentation process. First,efficient C4 ALA synthesis pathway was established in C. glutamicum by over-expressing the ALA synthase（ALAS）from Rhodopseudomonas palustris. Then,the ALA fermentation process with flask was optimized from four factors：fermentation medium,concentration of inducer,substrate concentration,and initial inoculum dosage. As results,the ALA yield of the strain 13032/pZWA1 over-expressing HemA was 1.41 g/L,up to 67.14 folds compared with the control strain. The optimal ALA fermentation condition was M9 media using yeast extract as nitrogen source with 5% inoculum size,0.1 mmol/L IPTG to induce the experession of HemA,and the concentration of glycine must be at 4 g/L. After optimization,ALA yield reached 3.28 g/L in a shaking flask and increased 132.62% than before. In conclusion,under the optimal fermentation condition,the ALA yield in a 5 L bioreactor fermentation was 10.08 g/L,which was the highest ALA yield by one-step fermentation of C. glutamicum reported so far.

Key words: 5-aminolevulinic acid, Corynebacterium glutamicum, 5-aminolevulinic acid synthetase, Rhodopseudomonas palustris ATCC17001, optimization of fermentation