CONSTANT-VOLUME FED-BATCH OPERATION FOR HIGH-DENSITY CULTIVATION OF HYPERTHERMOPHILIC AEROBES

When hyperthermophilic archaebacteria are cultivated under aerobic con ditions, the loss of the culture volume becomes significant due to vap orization of water with aeration. To eliminate the problems caused by evaporation of the medium, we have devised a constant-volume fed-batch system, where the loss of water due to evaporation is compensated by feeding additional water into the fermenter. The feeding strategy for maintaining a constant volume during fed-batch cultivation was develop ed from the water balance and the cell growth and substrate consumptio n kinetics, and the developed method was applied to high density culti vation of Sulfolobus solfataricus DSM 1617. The maximum cell density o btained was 22.6 g/L, which is the highest value reported for hyperthe rmophiles in fed-batch operations.