C4- dicarboxylic acids are the key potential building blocks for deriving commodity and specialty chemicals from biomass. Most engineered E.coli strains constructed for C4 acids formation, however, suffer from severe growth defects. Our studies were directed at determining if library overexpression was effective at improving the growth of NZN111- a succinic acid production strain.  We found that altered internal redox balance was responsible for the growth inhibition of this strain.  Using SCALEs, a genome wide approach, we identified a number of genetic changes that can balance the redox inside the cell.  Based on this genetic information, we modified the growth media and observed two-fold improvement in succinic acid production and four-fold improvement in growth for NZN111. Extending this approach to AFP111, a derivative of NZN111, resulted in further improvements in succinic acid productivity.