Enhancement of recombinant protein production in Escherichia coli by coproduction of aspartase

As commonly recognized, the excretion of acetate by the aerobic growth of Escherichia coli on glucose is a manifestation of imbalanced flux between glycolysis and the tricarboxylic acid (TCA) cycle. Accordingly, this may restrict the production of recombinant proteins in E. coli, due to the limited amounts of precursor metabolites produced in TCA cycle. To approach this issue, an extra supply of intermediate metabolites in TCA cycle was made by conversion of aspartate to fumarate, a reaction mediated by the activity of l-aspartate ammonia-lyase (aspartase). As a result, in the glucose minimal medium containing aspartate, the production of two recombinant proteins, β-galactosidase and green fluorescent protein, in the aspartase-producing strain was substantially increased by 5-fold in association with 30–40% more biomass production. This preliminary study illustrates the great promise of this approach used to enhance the production of these two recombinant proteins.