H
2 production under aerobic conditions has been proposed as an alternative method to overcome the fundamentally low yield of H
2 production by fermentative bacteria by maximizing the number of electrons that are available for H
2. Here, we engineered
Vitreoscilla hemoglobin (VHb) in
Escherichia coli to study the effects of this versatile oxygen (O
2)-binding protein on oxic H
2 production in a closed batch system that was supplemented with glucose. The H
2 yields that were obtained with the VHb-expressing
E. coli were greatly enhanced in comparison to the negative control cells in culture that started with high O
2 tensions. The formate hydrogen lyase (FHL) activity of oxically cultured, VHb-expressing cells was also much higher than that of the negative control cells. Through inhibitor studies and time-course experiments, VHb was shown to contribute to the improved H
2 yield primarily by increasing the efficiency of cellular metabolism during the aerobic phase before the onset of H
2 production and not by working as an O
2-scavenger during H
2 production. This new approach allowed more substrate to remain to be further utilized for the production of more H
2 from limited resources. We expect that VHb can be successfully engineered in potential aerobic H
2-producing microbial systems to enhance the overall H
2 production yield. In addition, the remarkably high FHL activity of oxically grown, VHb-expressing cells may make this engineered strain an attractive whole-cell biocatalyst for converting formate to H
2.
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