Efficient aerobic succinate production from glucose in minimal medium with Corynebacterium glutamicum.

ABSTRACT

Corynebacterium glutamicum, an established industrial amino acid producer, has been genetically modified for efficient succinate production from the renewable carbon source glucose under fully aerobic conditions in minimal medium. The initial deletion of the succinate dehydrogenase genes (sdhCAB) led to an accumulation of 4.7 g l(-1) (40 mM) succinate as well as high amounts of acetate (125 mM) as by-product. By deleting genes for all known acetate-producing pathways (pta-ackA, pqo and cat) acetate production could be strongly reduced by 83% and succinate production increased up to 7.8 g l(-1) (66 mM). Whereas overexpression of the glyoxylate shunt genes (aceA and aceB) or overproduction of the anaplerotic enzyme pyruvate carboxylase (PCx) had only minor effects on succinate production, simultaneous overproduction of pyruvate carboxylase and PEP carboxylase resulted in a strain that produced 9.7 g l(-1) (82 mM) succinate with a specific productivity of 1.60 mmol g (cdw)(-1) h(-1). This value represents the highest productivity among currently described aerobic bacterial succinate producers. Optimization of the production conditions by decoupling succinate production from cell growth using the most advanced producer strain (C. glutamicumΔpqoΔpta-ackAΔsdhCABΔcat/pAN6-pyc(P458S) ppc) led to an additional increase of the product yield to 0.45 mol succinate mol(-1) glucose and a titre of 10.6 g l(-1) (90 mM) succinate.