Central pathway engineering for enhanced succinate biosynthesis from acetate in <i>Escherichia coli</i>

Acetate, a non-food based substrate obtained from multiple biological and chemical ways, is now being paid great attention in bio-manufacturing and have a strong potential to compete with sugar-based carbon source. In this study, acetate can be efficiently converted to succinate by engineered Escherichia coli strains via the combination of several metabolic engineering strategies, including reducing OAA decarboxylation, engineering TCA cycle, enhancement of acetate assimilation pathway and increasing aerobic ATP supply through cofactor engineering. The engineered strain HB03(pTrc99a-gltA, pBAD33-Trc-fdh) accumulated 30.9 mM of succinate in 72 hr and the yield reached the maximum theoretical yield (∼0.50 mol/mol). In the resting-cell experiments, the yield of succinate in HB03(pTrc99a-gltA) and HB03(pTrc99a-gltA, pBAD33-Trc-fdh) dropped dramatically, although the productivity of succinate increased due to the high cell density. Further deletion of icdA, formed HB04(pTrc99a-gltA) and HB04(pTrc99a-gltA, pBAD33-Trc-fdh), increased the yield of succinate in the resting-cell experiments. The highest concentration of succinate achieved 194 mM and the yield reached 0.44 mol/mol in 16 hr by HB04(pTrc99a-gltA, pBAD33-Trc-fdh). The results showed the metabolically engineered E. coli strains have great potential to produce succinate from acetate.