CONTINUOUS CULTIVATION OF HYDROGENOBACTER-THERMOPHILUS AT LOW PARTIALPRESSURES OF H-2

Growth of the thermophilic H-2-oxidizing bacterium Hydrogenobacter the rmophilus (ITI 553) was achieved in continuous culture using a gas-lif t bioreactor. Although the highest equilibrium cell density was obtain ed at a dilution rate of 0.05 h(-1), the maximum productivity was obta ined at 0.1 h(-1). At 0.05 h(-1), the maintainable cell density was 7. 10(8) cells/ml at 2-4% oxygen with a gas flow rate of 0.1 vvm. The ste ady-state cell density increased further with increasing gas flow rate s. Maximum specific activity of the peroxidase was obtained at 8% oxyg en. The total productivity of the enzyme had its maximum at 6-8% oxyge n. Increasing gas flow rates had hardly any effect upon peroxidase spe cific activity, however, productivity was increased due to the increas ed cell densities obtained.