Co-expression of Bacterial Hemoglobin Improves Recombinant Expression of Carbonic Anhydrase in <i>Escherichia coli</i>

Carbonic anhydrase (CA) is a zinc-containing enzyme that catalyzes the CO 2 hydration reaction.CA has gained much attention as a green and sustainable biocatalyst to accelerate CO 2 capture and utilization.For industrial applications, it is desirable to reduce the enzyme production cost by improving the recombinant production of CA.Vitreoscilla hemoglobin (VHb) is a bacterial hemoglobin whose heterologous expression in Escherichia coli can improve cellular respiration and thereby recombinant protein production.In this study, Neisseria gonorrhoeae CA (NgCA) as a model CA was co-expressed with VHb in E. coli to improve the production of NgCA.When the VHb co-expression was controlled by the hypoxia-inducible Nar promoter, no visible VHb expression nor improvement in NgCA production was observed.In contrast, the bicistronic expression of VHb along with NgCA by the isopropyl--D-thiogalactopyranoside-inducible Trc promoter improved the expression level of NgCA by 15%-18%.The activity of purified NgCA was not affected by the VHb co-expression.Thus, the VHb co-expression should have general use as an effective strategy to increase the bacterial production of industrially relevant CA enzymes.