A significantly improved, recombinant Escherichia coli has been developed to degrade the toxic organophosphorus compound, Paraoxon, to non-toxic materials by co-expression of organophosphorus hydrolase (OPH) under trc promoter and Vitreoscilla hemoglobin (VHb) under O-2 dependent nar promoter. VHb-expressing whole cells had significant enhancement of OPH activity (48%, 18.7 vs. 27.8 unit l(-1)) and bioconversion efficiency V-max/K-m (44%, 0.14 vs. 0.2 min(-1)) compared to VHb-free system.