Effect of different levels of NADH availability on metabolic fluxes of Escherichia coli chemostat cultures in defined medium

In the current study, it was found that higher NADH yields and NADH/NAD+ ratios were achieved with our in vivo NADH regeneration system compared to a control lacking the new FDH pathway in the three carbon sources (glucose, gluconate and sorbitol) examined suggesting a more reduced intracellular environment. The total NAD(H/+) amounts were very similar for all the combinations studied. It was also found that the ethanol to acetate ratio increased with increased NADH availability. This ratio increased from 1.05 for the control strain in glucose to 9.45 for the strain expressing the heterologous NAD+-dependent FDH in sorbitol.