Alteration of reducing powers in an isogenic phosphoglucose isomerase (pgi)-disrupted Escherichia coli expressing NAD(P)-dependent malic enzymes and NADP-dependent glyceraldehyde 3-phosphate dehydrogenase.

To understand the intracellular reducing power metabolism, growth and intracellular NAD(P)H concentrations of a phosphoglucose isomerase (pgi)-disrupted Escherichia coli (KS002) were investigated with the expressions of redox enzymes. The isogenic pgi-mutation enabled E. coli to harbour two times both the intracellular NADPH and NADH at half the growth rate. The wild-type expressing NAD-dependent malic enzyme (maeA) was incapable of sufficient growth (<0·02 h(-1)), and the growth retardations were distinctively recovered when NADP-dependent glyceraldehyde-3-phosphate dehydrogenase (gapB) from Bacillus subtilis was coexpressed. The KS002 expressing maeA harboured the highest intracellular reducing powers (NADPH of 3·9 and NADH of 5·2 μmol g DCW(-1) ) by three times each of those in wild type. The expression of NADP-dependent malic enzyme (maeB) enabled wild-type and KS002 strains to grow without significant alteration. The alterations of reducing powers and the growth were analysed in the genetic engineered E. coli strains. The potential application of the cells with the high intracellular NAD(P)H level is discussed based on the results. Metabolic engineering strategy for higher reducing power regeneration is provided.