Continuous cultivation of Hydrogenobacter thermophilus at low partial pressures of H

Growth of the thermophilic H-oxidizing bacterium Hydrogenobacter thermophilus (ITI 553) was achieved in continuous culture using a gas-lift bioreactor. Although the highest equilibrium cell density was obtained at a dilution rate of 0.05 h, the maximum productivity was obtained at 0.1h. At 0.05 h, the maintainable cell density was 7.10 cells/mL at 2-4% oxygen with a gas flow rate of 0.1vvm. The steady-state cell density increased further with increasing gas flow rates. Maximum specific activity of the peroxidase was obtained at 8% oxygen. The total productivity of the enzyme had its maximum at 6-8% oxygen. Increasing gas flow rates had hardly any effect upon peroxidase specific activity, however, productivity was increased due to the increased cell densities obtained.