Production of biohydrogen by heterologous expression of oxygen-tolerant Hydrogenovibrio marinus [NiFe]-hydrogenase in Escherichia coli

Oxygen sensitivity of hydrogenase is a critical issue in efficient biological hydrogen production. In the present study, oxygen-tolerant [NiFe]-hydrogenase from the marine bacterium, Hydrogenovibrio marinus, was heterologously expressed in Escherichia coli, for the first time. Recombinant E. coli BL21 expressing H. marinus [NiFe]-hydrogenase actively produced hydrogen, but the parent strain did not. Recombinant H. marinus hydrogenase required both nickel and iron for biological activity. Compared to the recombinant E. coli [NiFe]-hydrogenase 1 described in our previous report, recombinant H. marinus [NiFe]-hydrogenase displayed 1.6- to 1.7-fold higher hydrogen production activity in vitro. Importantly, H. marinus [NiFe]-hydrogenase exhibited relatively good oxygen tolerance in analyses involving changes of surface aeration and oxygen proportion within a gas mixture. Specifically, recombinant H. marinus [NiFe]-hydrogenase produced ∼7- to 9-fold more hydrogen than did E. coli [NiFe]-hydrogenase 1 in a gaseous environment containing 5-10% (v/v) oxygen. In addition, purified H. marinus [NiFe]-hydrogenase displayed a hydrogen evolution activity of ∼28.8 nmol H₂/(min mg protein) under normal aerobic purification conditions. Based on these results, we suggest that oxygen-tolerant H. marinus [NiFe]-hydrogenase can be employed for in vivo and in vitro biohydrogen production without requirement for strictly anaerobic facilities.