Effects of inactivation of acetate synthetic pathway genes and overexpression of NADH oxidase on acetoin production in Corynebacterium glutamicum

Abstract:

[Objective] We researched the effects of inactivation of acetate synthetic pathway and expression of NADH oxidase on acetoin production in Corynebacterium glutamicum. [Methods] Heterologous expression of alsSD operon in C. glutamicum CGF2 resulted in acetoin production strain CGT1, and disruption of acetate synthetic pathway gene cat and pqo was investigated. Subsequently, NADH oxidase from Lactobacillus brevis was developed for acetoin production under optimal oxygen condition. [Results] CGT1 accumulated 6.27 g/L acetoin in flask cultivation. Deletion of cat increased acetion production by 30.94% compared with CGT1, which was 8.21 g/L. Deletion of cat and pqo had no improvement on production. Moreover, the production of acetoin enhanced 10.06 g/L by optimizing the concentration of dissolved oxygen. Under high dissolved oxygen, expression of NADH oxidase contributed to an increase in biomass and glucose consumption rate, but the titer of acetoin decreased slightly. In intermittent fed-batch fermentation, recombination strain produced 40.51 g/L acetoin with a productivity of 0.51 g/(L?h). [Conclusion] The inactivation of acetate synthetic pathway gene cat could efficiently increase the production of acetoin in C. glutamicum. However, expression of NADH oxidase had disadvantage of acetion, and its expression level required more regulation to confirm the effect.