Continuous hydrogen production by the hyperthermophilic archaeon, Thermococcus kodakaraensis KOD1

The hydrogen (H-2) production potential of the hyperthermophilic archaeon, Thermococcus kodakaraensis KOD1 was evaluated at 85 degreesC. In batch cultivation using a complex medium supplemented with elemental sulfur (S-0), evolution of H2S and CO2 was observed in the gas phase. When So was omitted and pyruvate or starch was added in the medium, the cells produced H-2 at high levels instead of H2S. As the level of H-2 appeared to correlate with the specific growth rate, analysis in continuous cultures was performed to develop a continuous H-2 production system. In a steady-state condition at a dilution rate of 0.2 h(-1), a continuous H-2 production rate (per gram dry weight, gdw) of 24.9 and 14.0 mmol gdw(-1) h(-1) was observed in media supplemented with pyruvate and starch, respectively. In both cultivations, a high accumulation of acetate and alanine was found as metabolites. When the dilution rates were elevated in the medium with pyruvate, steady-state growth was observed up to 0.8 h(-1), and a maximum H-2 production rate of 59.6 mmol gdw(-1) h(-1) was obtained. Based on the experimental results along with data of the entire genome sequence, the metabolic pathway of the strain relating to starch and pyruvate degradation is discussed. (C) 2004 Elsevier B.V. All rights reserved.