Co-expression of Vitreoscilla hemoglobin (VHb) can enhance production of foreign proteins in several microorganisms, including Escherichia coli. Production of foreign proteins [ green fluorescent protein (GFP) and organophosphorous hydrolase (OPH)] has been examined in two typical industrial E. coli strains, W3110 (a K12 derivative) and BL21 ( a B derivative). In particular, we investigated the effects of VHb co-expression and media glucose concentration on target protein production. We employed the nar O-2-dependent promoter for self-tuning of VHb expression based on the natural changes in dissolved O-2 levels over the duration of culture. Foreign protein production in strain BL21 was decreased by a high glucose concentration but co-expression of VHb had no effect on this. In contrast, co-expression of VHb in strain W3110 overrode the glucose-induced repression and resulted in steady expression of foreign proteins.