Escherichia coli strains were developed for the fermentative production of succinate from glucose in mineral salts medium by a combination of deliberate gene deletions to inactivate competing routes for fermentative NADH oxidation and metabolic evolution using growth-based selection. Resulting strains fermented glucose into succinate at yields and titers equivalent to the highest levels reported for rumen bacteria. Three significant changes in metabolism that increased energy efficiency were characterized during metabolic evolution. (1) Phosphoenolpyruvate (PEP) carboxykinase, an enzyme that normally functions in gluconeogenesis (decarboxylation direction, glucose repressed), was recruited (promoter mutation) to serve as the dominant carboxylation pathway leading to an increase in net ATP. (2) The native PEP-dependent phosphotransferase system for glucose was disrupted by a mutation in ptsI.  (3) An alternative glucose utilization pathway (galP and glk) was recruited to replace the native PTS system for glucose, increasing PEP pool available for redox balance and eliminating a need to regenerate PEP from ATP and pyruvate. Subsequent studies demonstrated that  these core mutations were sufficient to substantially redirect the fermentative metabolism of glucose to succinate in wild type E. coli even without the deletion of native pathways for mixed acid fermentation. The newly engineered succinate pathway in E. coli is functionally equivalent to the native pathway in succinate-producing rumen bacteria. These energy-conserving strategies can also be applied to other important problems in metabolic engineering.