Enhanced Production of 5-aminolevulinic Acid via Flux Redistribution of TCA Cycle toward L-Glutamate in Corynebacterium glutamicum

摘要

5-Aminolevulinic acid (ALA), a valuable nonproteinogenic amino acid, has received increasing attention in various fields including medicine, agriculture, and cosmetics. Here, we developed metabolically engineered Corynebacterium glutamicum to enhance ALA production. To achieve this object, we focused on the flux redistribution of the TCA cycle toward l-glutamate and introduction of the heterogenous ALA transporter in C. glutamicum. First, the oxoglutarate dehydrogenase inhibitor (OdhI) was mutated by site-directed mutagenesis to prevent the phosphorylation that abolishes the capability of OdhI protein to inhibit oxoglutarate dehydrogenase complex activity. The overexpression of the double-mutated OdhI, T14A/T15A, showed the highest l-glutamate and ALA production compared with that of the native and single-mutated OdhI. To increase ALA secretion from the engineered strain, the ALA exporter RhtA from Escherichia coli was introduced and allowed 2.46 +/- 0.11 g/L of ALA production, representing a 1.28-fold increase in extracellular ALA production. In the final strain, the induction of triggers, including Tween 40 and ethambutol, was performed to amplify the effect of the flux redistribution toward ALA. A significant increase in ALA production was observed in the induction of triggers. In particular, ethambutol induction showed the best result, corresponding to 2.9 +/- 0.15 g/L of ALA production. Therefore, this biotechnological model enables the efficient extracellular production of ALA from glucose in C. glutamicum.