Abstract
The membrane-bound hydrogenase from a marine hydrogen-oxidizing bacteriumHydrogenovibrio marinuswas characterized as highly oxygen-tolerant, extremely thermophilic and thermostable in its membrane-bound form. The optimum temperatures for H2oxidation and H2evolution were 90 and 80°C, respectively. The enzyme retained 90% of its activity after heating at 70°C for 50 min under air and retained full activity at 90°C for 80 min under hydrogen. The optimum pH values were 5.5 (H2evolution) and 9.4 (H2oxidation), and the activity ratio (H2evolution/H2oxidation) was high (50.3) at pH 5.5. The hydrogen evolution from reduced methyl viologen continued at high temperatures and acidic pH with the continuous addition of sodium dithionite.
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