GROWTH-CHARACTERISTICS AND HIGH CELL-DENSITY CULTIVATION OF A MARINE OBLIGATELY CHEMOLITHOAUTOTROPHIC HYDROGEN-OXIDIZING BACTERIUM HYDROGENOVIBRIO-MARINUS STRAIN MH-110 UNDER A CONTINUOUS GAS-FLOW SYSTEM

A marine obligately chemolithoautotrophic aerobic hydrogen-oxidizing bacterium Hydrogenovibrio marinus strain MH-110 was cultivated in a 2-l jar fermentor with continuous supply of a mixed gas of H-2/O2 /CO2. Fast growth began rapidly without a lag period, even in an atmosphere of 40% oxygen. Apparent specific growth rate of the initial stage of growth was 0.60-0.67 h-1 irrespective of any oxygen tension tested. Under an atmosphere containing hydrogen, the growth was promoted by the addition of tetrathionate to the medium. A dense culture was achieved by increasing the tension of oxygen and adding ferrous and magnesium ions before these factors became growth limiting. Under this culture condition, exponential growth continued until the cell density reached 14 g/l dry weight. The final cell concentration reached approximately 26 g/l dry weight after 30-h cultivation.