Fig. 1
Metabolic network of E. coli under anaerobic conditions and metabolic engineering strategies for succinate overproduction. Modified genes for improving succinate yield are highlighted in bold. X indicates metabolic reactions that have been blocked by gene deletions. Dotted arrows indicate steps that are heterogeneously expressed in E. coli. Genes and enzymes: ldhA encoding lactate dehydrogenase; pflB encoding pyruvate-formate lyase; pta encoding phosphate acetyltransferase; ackA encoding acetate kinase; adhE encoding alcohol dehydrogenase; ppc encoding phosphoenolpyruvate carboxylase; pepck encoding phosphoenolpyruvate carboxykinase; pyc encoding pyruvate carboxylase; aceEF-lpd encoding pyruvate dehydrogenase complex; mdh encoding malate dehydrogenase; fumA, fumB, and fumC encoding fumarase isozymes; frdABCD encoding fumarate reductase; galp encoding galactose permease; glk encoding glucokinase; PTS phosphotransferase systems; zwf243 encoding 6-phosphate dehydrogenase; gnd361 encoding 6-phosphogluconate dehydrogenase; pgl encoding 6-phosphogluconolactonase; tktA encoding transketolase; talB encoding transaldolase; sthA encoding soluble transhydrogenase