A wide range of microorganisms, from photoautotrophs to heterotrophs, can generate molecular hydrogen (H
2). The hyperthermophilic archaeon,
Thermococcus kodakarensis KOD1, is one such organism, an anaerobic heterotroph that grows optimally at 85 °C. The H
2-producing potential of this organism was evaluated in a complex medium supplemented with either pyruvate or starch. In a continuous culture using pyruvate, the H
2-production rate (per gram dry weight per hour) was 59.6 mmol g
−1 h
−1 at a dilution rate of 0.8 h
−1, indicating that
T. kodakarensis exhibits one of the highest H
2-production rates among microorganisms so far examined. Our efforts are now focused on understanding the mechanisms governing H
2 production in this organism, which should also lead to strategies to further enhance productivity. The
T. kodakarensis genome contains three gene clusters that encode [NiFe]-hydrogenase orthologs, Hyh, Mbh and Mbx. Analysis of the phenotypes of individual gene disruption strains revealed that Mbh is the hydrogenase responsible for H
2 evolution, whereas Hyh and Mbx participate in H
2 consumption and H
2S production, respectively. Therefore, enhancing the function of Mbh and eliminating the function of Hyh should be effective in developing a strain with increased H
2-generation capacity.
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