Engineering Corynebacterium crenatum for enhancing succinic acid production

Succinic acid is valuable due to its historical use in food industry. In this paper, Corynebacterium crenatum was engineered to enhance succinic acid production and the fermentation properties of engineered strains were investigated. The lactate dehydrogenase gene (ldhA) inactivation mutant was first constructed, and then the pyruvate carboxylase gene (pyc) or phosphoenolpyruvate carboxylase gene (ppc) was expressed in the ldhA mutant. The ldhA inactivation resulted in a 52% decrease on glucose consumption, and the succinic acid yield produced by the ldhA mutant was 0.62 g/g, representing a 2-fold increase compared with the yield obtained from the original strain. Overexpression of pyc gene could improve the glucose consumption rate, resulting in a 37% increase compared with the ldhA mutant strain. Meanwhile, the final succinic acid concentration represented a 50% increase than the ldhA mutant strain, and a 106% increase than the original strain. Overexpression of ppc gene had no significant effect.