Constant-volume fed-batch operation for high density cultivation of hyperthermophilic aerobes

Abstract

When hyperthermophilic archaebacteria are cultivated under aerobic conditions, the loss of the culture volume becomes significant due to vaporization 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 developed from the water balance and the cell growth and substrate consumption kinetics, and the developed method was applied to high density cultivation of Sulfolobus solfataricus DSM 1617. The maximum cell density obtained was 22.6 g/L, which is the highest value reported for hyperthermophiles in fed-batch operations.